Nodular Fasciitis
Clinical Features
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Primarily affects young adults aged 20 to 40 years; occasionally seen in children
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Presents as a rapidly growing solitary mass; may be painful
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Inconsistently associated with recognized previous trauma (10% to 15%)
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Can involve any site; flexor aspect of forearm, chest, and back are common sites
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Spontaneous regression is expected
Gross Pathology
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Located in the deep dermis or subcutis; occasionally occurs intramuscularly
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Round to oval, nodular, well-circumscribed mass; usually smaller than 3 cm
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Cut surface may be fibrous, myxoid, or cystic
Histopathology
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Usually well circumscribed but occasionally infiltrative
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“Tissue culture” appearance with long fascicles of spindled cells with a whorled growth pattern; extravasated red blood cells are a helpful feature ( Figure 17.1 )
Figure 17.1
Nodular fasciitis.
Bland plump spindle cells with a “tissue culture” appearance are present in a myxoid to collagenous stroma with admixed inflammatory cells and extravasated RBCs.
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Newer lesions have a loose, feathery collagenous stroma with myxoid or microcystic appearance, whereas older lesions are less cellular and more densely collagenized
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Zonal pattern with cellular periphery and loose, feathery center that may be cystic
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Scattered inflammatory cells, typically lymphocytes and macrophages
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Occasional mitotic figures; no abnormal mitotic figures
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Variants
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Intravascular fasciitis
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Primarily affects children and adolescents
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Involves arteries and veins
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Cranial fasciitis
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Affects infants younger than 1 year
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Involves the scalp and skull
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Ossifying fasciitis
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Often shows osseous metaplasia
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Periosteal location
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Similar to myositis ossificans but lacks triphasic zonal pattern
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Special Stains and Immunohistochemistry
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Vimentin and smooth muscle actin (SMA) positive
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Immunohistochemistry does not help to exclude other myofibroblastic or smooth muscle proliferations
Other Techniques For Diagnosis
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Translocation t(17;22)(p13;q13.1), producing a MYH9-USP6 fusion demonstrable by molecular or in situ hybridization studies, typically cryptic by karyotype
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Only seen in nodular fasciitis, not its variants
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Differential Diagnosis
Kaposi Sarcoma
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Ill-defined margins
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Prominent vasculature, extravasated red blood cells
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Found in immunocompromised individuals; typically patients with acquired immunodeficiency syndrome (AIDS)
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Immunoreactive for human herpesvirus type 8 (HHV-8) latent nuclear antigen 1 (LANA-1), and endothelial markers
Myxoma
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Characterized by a paucity of cells, myxoid matrix, and sparse vascularity
Fibrous Histiocytoma (Dermatofibroma)
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Spindle cell proliferation admixed with epithelioid and foamy histiocytes
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Typically arranged in a storiform pattern
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Lacks prominent vasculature and extravasated red blood cells
Fibromatosis (Desmoid Tumor)
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Dense collagenous stroma usually lacking inflammatory component
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Lacks thin-walled vessels
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Nuclear immunoreactivity for β-catenin in most cases
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Nodular fasciitis is commonly misdiagnosed as a sarcoma
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Confirmed as a neoplastic condition
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Benign lesion with an excellent prognosis
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May progress through myxoid, cellular, and fibrous phases
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Conservative surgical resection is the treatment of choice, but close follow-up is also acceptable
Selected References
Amary M.F., Ye H., Berisha F., Tirabosco R., et. al.: Detection of USP6 gene rearrangement in nodular fasciitis: an important diagnostic tool. Virchows Arch 2013; 463: pp. 97-98.
Erickson-Johnson M.R., Chou M.M., Evers B.R., et. al.: Nodular fasciitis: a novel model of transient neoplasia induced by MYH9-USP6 gene fusion. Lab Invest 2011; 91: pp. 1427-1433.
Montgomery E.A., Meis J.M.: Nodular fasciitis: its morphologic spectrum and immunohistochemical profile. Am J Surg Pathol 1991; 15: pp. 942-948.
Price E.B., Sillaphant W.M., Shuman R.: Nodular fasciitis: a clinicopathologic analysis of 65 cases. Am J Clin Pathol 1961; 35: pp. 122-136.
Sarangarajan R., Dehner L.P.: Cranial and extracranial fasciitis of childhood: a clinicopathologic and immunohistochemical study. Hum Pathol 1999; 30: pp. 87-92.
Proliferative Fasciitis and Myositis
Clinical Features
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Typically occurs in adults (usually about 50 years of age)
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Firm, palpable, rapidly growing subcutaneous or intramuscular nodule; may be painful
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Proliferative fasciitis
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Most common site is forearm, followed by leg and trunk
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Often associated with a history of trauma
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Proliferative myositis
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Commonly located in the flat muscles of the trunk and shoulder girdle
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Gross Pathology
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Poorly circumscribed, gray-white soft tissue mass
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Typically measures 1 to 3 cm in diameter
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Proliferative myositis is commonly a pale, gray, scarlike induration involving muscle and overlying fascia
Histopathology
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Ill-defined lesions characterized by large myofibroblasts that have large vesicular nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm (ganglion-like cells) admixed with immature spindle cells in a matrix composed of varying proportions of mucoid material and collagen
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Often numerous mitotic figures in spindled and ganglion-like cells; they are not atypical ( Figure 17.2 )
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Proliferative fasciitis
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Typically grows along fibrous septa between fat lobules
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Proliferative myositis
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Endomysial and epimysial growth separates bundles of atrophic skeletal muscle, creating a checkerboard pattern
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Figure 17.2
Proliferative fasciitis.
Numerous ganglion-like cells are seen in a collagenous stroma.
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Special Stains and Immunohistochemistry
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Ganglion-like cells are often nonreactive toward muscle markers and react with vimentin only
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Rhabdomyosarcoma
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Tumor of children, rarely seen in adults
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Presence of rhabdomyoblasts rarely with cytoplasmic cross-striations
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Immunoreactivity for desmin, muscle-specific actin (MSA), myogenin, and MyoD1
Ganglioneuroblastoma
- •
Intermixed neuroblasts and ganglion cells in a background of Schwannian spindle cell stroma
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S100 protein is present in the Schwannian stroma
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Tumor of young children; extremities an unusual location
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Pathogenesis of proliferative fasciitis and myositis remains unexplained; fascial or muscular injury is thought to be a likely contributor
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Benign, self-limited, reactive process treated with conservative surgical excision
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Proliferative fasciitis and proliferative myositis are similar reactive proliferations that are best distinguished by their locations
Selected References
Chung E.B., Enzinger F.M.: Proliferative fasciitis. Cancer 1975; 36: pp. 1450-1458.
El-Jabbour J.N., Bennett M.H., Burke M.M., et. al.: Proliferative myositis: an immunohistochemical and ultrastructural study. Am J Surg Pathol 1991; 15: pp. 654-659.
Enzinger F.M., Dulcey F.: Proliferative myositis: report of thirty-three cases. Cancer 1967; 20: pp. 2213-2223.
Meis J.M., Enzinger F.M.: Proliferative fasciitis and myositis of childhood. Am J Surg Pathol 1992; 16: pp. 364-372.
Wong N.L.: Fine needle aspiration cytology of pseudosarcomatous reactive proliferative lesions of soft tissue. Acta Cytol 2002; 46: pp. 1049-1055.
Myositis Ossificans
Clinical Features
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Commonly affects young, athletic adults; usually involves the extremities
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Uncommon in children
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Presents as a solitary, tender mass; often associated with a history of trauma (>50% of cases)
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Radiographic findings show characteristic zonal ossification, with rapid mineralization evident on sequential studies
Gross Pathology
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Well-circumscribed, gray-yellow lesions with gritty areas
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Some cases have central blood-filled spaces and are regarded as a variant of aneurysmal bone cyst occurring outside of bone ( Figure 17.3 )
Figure 17.3
Myositis ossificans/aneurysmal bone cyst of soft tissue.
In this variant of myositis ossificans, a rim of bone is present around a central hemorrhagic cyst.
Histopathology
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Typically shows a triphasic pattern with distinct zonation
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Central cellular region
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Resembles nodular fasciitis
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Cells have bland nuclear features and a variable mitotic rate
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Occasional multinucleated giant cells
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- •
Intermediate region is composed of immature osteoid
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Peripheral zone is composed of mature, “purposeful” lamellar bone
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Cartilage may be present
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- •
Special Stains and Immunohistochemistry
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Noncontributory
Other Techniques for Diagnosis
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USP6 translocation is detectible by fluorescence in situ hybridization (FISH) in some cases
Differential Diagnosis
Extraskeletal Osteosarcoma
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Characterized by disordered growth of hyperchromatic, pleomorphic cells with delicate lacelike osteoid formation, often with faint bluish calcification
- •
Absence of zonation
Ossifying Fibromyxoid Tumor
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Chords and aggregates of plump spindle cells in a fibromyxoid matrix, with osteoblastic differentiation and bone formation generally around the outer rim of the tumor
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Lacks inflammatory cells and granulation tissue appearance
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Myositis ossificans is a benign, self-limited process with an excellent prognosis
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Spontaneous regression can occur
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A subset, likely those with USP6 translocation, have features of aneurysmal bone cyst
Selected References
Ackerman L.V.: Extra-osseous localized non-neoplastic bone and cartilage formation (so-called myositis ossificans): clinical and pathological confusion with malignant neoplasms. J Bone Joint Surg Am 1958; 40: pp. 279-298.
Clapton W.K., James C.L., Morris L.L., et. al.: Myositis ossificans in childhood. Pathology 1992; 24: pp. 311-314.
Nuovo M.A., Norman A., Chumas J., et. al.: Myositis ossificans with atypical clinical, radiographic, or pathologic findings: a review of 23 cases. Skeletal Radiol 1992; 21: pp. 87-101.
Wilson J.D., Montague C.J., Salcuni P., et. al.: Heterotopic mesenteric ossification (“intraabdominal myositis ossificans”): report of five cases. Am J Surg Pathol 1999; 23: pp. 1464-1470.
Zhang L., Hwang S., Benayed R., et. al.: Myositis ossificans-like soft tissue aneurysmal bone cyst: a clinical, radiological, and pathological study of seven cases with COL1A1-USP6 fusion and a novel ANGPTL2-USP6 fusion. Mod Pathol 2020; 33: pp. 1492-1504.
Ischemic Fasciitis
Clinical Features
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Also referred to as atypical decubital fibroplasia
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Occurs over bony prominences or other pressure points in debilitated patients
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Almost exclusively seen in late adulthood and rarely in younger patients
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More commonly found in females
Gross Pathology
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Poorly circumscribed, multinodular mass up to 10 cm in diameter
- •
May have overlying ulceration
Histopathology
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Typical zonation pattern
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Central necrotic region
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Liquefactive or coagulative necrosis with fibrin deposition ( Figure 17.4 )
Figure 17.4
Ischemic fasciitis.
A transition is seen between fibrin-rich necrosis and stellate myofibroblastic cells.
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Peripheral fibroblastic and vascular proliferation
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Granulation tissue-like with plump endothelial cells
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Atypical fibroblasts with abundant eosinophilic cytoplasm and ganglion-like features
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Vascular thrombosis and fibrinoid necrosis
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- •
Special Stains and Immunohistochemistry
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Noncontributory
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Atypical Lipomatous Tumor
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Typical cases show scattered atypical cells present in adipose tissue with fibrous septa, which may resemble the reactive myofibroblasts in ischemic fasciitis
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Myxoid change may be extensive, making adipocytic component difficult to find, especially in small samples
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Fat necrosis is common, but not coagulative necrosis with fibrin
Bursitis
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May produce a mass with a central cavity, adjacent to a joint
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Cavity lining is generally denuded with fibrin exudate, and surrounded by inflammatory cells
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Ischemic fasciitis is a benign, reactive process likely related to intermittent ischemia
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Surgical excision is the treatment of choice; can recur owing to the persistence of the underlying cause
Selected References
Ilaslan H., Joyce M., Bauer T., Sundaram M.: Decubital ischemic fasciitis: clinical, pathologic, and MRI features of pseudosarcoma. Am J Roentgenol 2006; 187: pp. 1338-1341.
Liegl B., Fletcher C.D.: Ischemic fasciitis: analysis of 44 cases indicating an inconsistent association with immobility or debilitation. Am J Surg Pathol 2008; 32: pp. 1546-1552.
Perosio P.M., Weiss S.W.: Ischemic fasciitis: a juxta-skeletal fibroblastic proliferation with a predilection for elderly patients. Mod Pathol 1993; 6: pp. 69-72.
Elastofibroma
Clinical Features
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Usually presents as a deeply seated mass located in the lower subscapular area
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Almost exclusively seen in late adulthood and rarely in younger patients
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More commonly found in females
Gross Pathology
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Firm, rubbery soft tissue mass with ill-defined margins
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Cut surface is gray-white and glistening with entrapped foci of fat
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Focal cystic degeneration often seen
Histopathology
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Poorly defined lesion composed of thickened, coarse slightly basophilic elastic fibers and scant fibroblastic cells embedded in a heavily collagenized stroma ( Figure 17.5A )
Figure 17.5
Elastofibroma.
A, Gross photo of cut section (with the surface inked black) showing a poorly marginated gray-white mass. B, The tumor is paucicellular with bland fibroblasts and prominent elastic fibers in longitudinal and transverse cross section, evident on H&E (arrows) , highlighted by elastic stain (inset) .
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Entrapped mature adipose tissue is typically seen
Special Stains and Immunohistochemistry
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Verhoeff–van Gieson elastic stain: highlights elastic fibers ( Figure 17.5B )
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Fibrolipoma
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Characterized by predominance of mature adipocytes with intervening fibrous connective tissue
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Lacks elastic fibers
Spindle Cell Lipoma
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Subcutaneous mass in neck and shoulder region
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Ropy collagen present, but not prominent elastic fibers. May show extensive myxoid change and contain few to no adipocytes
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Histology of elastofibroma is described as “spaghetti and meatballs” owing to long and globular elastic fibers
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Increased incidence in manual laborers; related to repetitive motion injury
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Can usually be diagnosed by radiology or fine-needle aspiration
Selected References
Lococo F., Cesario A., Mattei F., et. al.: Elastofibroma dorsi: clinicopathological analysis of 71 cases. Thorac Cardiovasc Surg 2013; 61: pp. 215-222.
Vincent J., Maleki Z. Elastofibroma.: cytomorphologic, histologic, and radiologic findings in five cases. Diagn Cytopathol 2012; 40: pp. E99-E103.
Yamazaki K.: An ultrastructural and immunohistochemical study of elastofibroma: CD 34, MEF-2, prominin 2 (CD133), and factor XIIIa-positive proliferating fibroblastic stromal cells connected by Cx43-type gap junctions. Ultrastruct Pathol 2007; 31: pp. 209-219.
Superficial Fibromatoses
Clinical Features
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Presents as a small, slow-growing, subcutaneous nodule or thickening
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Palmar fibromatosis (Dupuytren contracture)
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Palmar surface of the hand; may result in contractures
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Almost exclusively in adults, males affected more than females
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Often bilateral, especially in alcoholics
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- •
Plantar fibromatosis (Ledderhose disease)
- •
Plantar, non-weight-bearing area of the foot
- •
Occurs in both children and adults
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Often multinodular
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- •
Penile fibromatosis (Peyronie disease)
- •
Dorsal aspect of the shaft of the penis
- •
Exclusively seen in adults
- •
- •
Gross Pathology
- •
Single or multiple, gray-white, firm nodules or scarlike tissue in the subcutis
Histopathology
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Proliferative and involutional phases
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Proliferative phase shows variably cellular fascicles of bland, spindled cells often arranged in a nodular pattern ( Figure 17.6 )
Figure 17.6
Superficial fibromatosis.
Dupuytren contracture. Area of transition between cellular and collagenous zones.
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Occasionally prominent giant cells in plantar lesions
- •
Mitotic figures may be seen
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Involutional or residual phase shows paucicellular, densely collagenized tissue
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Desmoid Type of Fibromatosis
- •
Rare in hands and feet
- •
Nuclear expression of beta-catenin is not helpful to distinguish between these entities
Fibroma of Tendon Sheath
- •
Well-circumscribed, sometimes multinodular mass firmly attached to tendon sheath
- •
Hypocellular with bland spindle cells widely separated by hyalinized collagenous stroma
Fibrosarcoma (Infantile and Adult Types)
- •
Infantile fibrosarcoma usually affects children younger than 1 year
- •
Adult fibrosarcoma is only rarely found in distal extremities
- •
Highly cellular, infiltrative tumor composed of uniform fibroblasts with hyperchromatic nuclei and scant cytoplasm, arranged in a distinctive herringbone pattern
- •
High mitotic rate is common; atypical mitotic figures may be seen
- •
Areas of necrosis or hemorrhage may be seen
- •
Superficial fibromatosis may be multifocal
- •
Plantar or palmar fibromatosis may be highly cellular and mistaken for sarcoma
- •
Associated conditions may include diabetes, cirrhosis, and epilepsy; some fibromatoses may have a hereditary component
- •
Surgical excision is the treatment of choice
Selected References
Allen P.W.: The fibromatoses: a clinicopathologic classification based on 140 cases. Am J Surg Pathol 1977; 1: pp. 255-270.
Evans H.L.: Multinucleated giant cells in plantar fibromatosis. Am J Surg Pathol 2002; 26: pp. 244-248.
Montgomery E., Lee J.H., Abraham S.C., et. al.: Superficial fibromatoses are genetically distinct from deep fibromatoses. Mod Pathol 2001; 14: pp. 695-701.
Fibrous Hamartoma of Infancy
Clinical Features
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Rapidly growing, painless subcutaneous mass in young children, sometimes congenital
- •
Common sites include trunk, shoulder, axilla, and groin
- •
Most cases occur within the first 2 years of life
Gross Pathology
- •
Poorly defined deep dermal or subcutaneous mass
- •
Gray, firm cut surface with yellow flecks
- •
Usually 2 to 5 cm but may be larger
Histopathology
- •
Triphasic appearance comprising an admixture of fibrous tissue, adipose tissue, and bundles of immature mesenchymal cells ( Figure 17.7 )
Figure 17.7
Fibrous hamartoma of infancy.
The triphasic population of collagen fascicles, primitive myoid bundles, and fat forms a stellate lesion.
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Often has a stellate configuration and infiltrates surrounding fat
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Lipofibromatosis
- •
Lacks a primitive mesenchymal component
Lipoblastoma
- •
Lobulated mass with fat lobules separated by fibrous bands
- •
Lacks a primitive mesenchymal component
- •
Myxoid stroma and lipoblasts are present
Embryonal Rhabdomyosarcoma
- •
Lacks fibrous and adipose tissue
- •
Positive for desmin, myogenin, and MyoD1
- •
Fibrous hamartoma of infancy is a benign lesion usually cured with local excision
Selected References
Coffin C.M., Dehner L.P.: Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients. Pediatr Pathol 1991; 11: pp. 569-588.
Dickey G.E., Sotelo-Avila C.: Fibrous hamartoma of infancy: current review. Pediatr Dev Pathol 1999; 2: pp. 236-243.
Groisman G., Lichtig C.: Fibrous hamartoma of infancy: an immunohistochemical and ultrastructural study. Hum Pathol 1991; 22: pp. 914-918.
Lipofibromatosis
Clinical Features
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Previously referred to as infantile fibromatosis, nondesmoid type
- •
Occurs in childhood, between birth and second decade; males affected more than females
- •
Slowly growing, painless mass most commonly presenting in an extremity or on the trunk; rare cases in the head and neck
- •
May cause isolated macrodactyly
Gross Pathology
- •
Poorly defined subcutaneous mass with admixed adipose tissue
- •
Usually 1 to 3 cm
Histopathology
- •
Bands of bland spindled cells and collagen traversing through mature adipose tissue ( Figure 17.8 )
Figure 17.8
Lipofibromatosis.
Fascicles of bland spindle cells and collagen are admixed with mature adipose tissue.
- •
Infiltrative borders
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Fibrous Hamartoma of Infancy
- •
Contains a primitive mesenchymal component
Lipoblastoma
- •
Lobulated mass with fat lobules separated by fibrous bands
- •
Myxoid stroma and presence of lipoblasts
Desmoid-Type Fibromatosis
- •
Contains moderately cellular areas of fibrous growth, which infiltrate into fat (or skeletal muscle); adipose tissue is not a primary component
- •
Lipofibromatosis has a high rate of local recurrence but no metastatic potential
- •
Wide local excision is the standard treatment
Selected References
Deepti A.N., Madhuri V., Walter N.M., et. al.: Lipofibromatosis: report of a rare paediatric soft tissue tumour. Skeletal Radiol 2008; 37: pp. 555-558.
Fetsch J.F., Miettinen M., Laskin W.B., et. al.: A clinicopathologic study of 45 pediatric soft tissue tumors with an admixture of adipose tissue and fibroblastic elements, and a proposal for classification as lipofibromatosis. Am J Surg Pathol 2000; 24: pp. 1491-1500.
Kenney B., Richkind K.E., Friedlaender G., et. al.: Chromosomal rearrangements in lipofibromatosis. Cancer Genet Cytogenet 2007; 179: pp. 136-139.
Calcifying Aponeurotic Fibroma
Clinical Features
- •
Also known as juvenile aponeurotic fibroma or Keasbey tumor
- •
Most commonly affects children but may also occur in adults
- •
Presents as a slow-growing, painless mass, usually on the palmar or plantar surfaces of the hands or feet, rarely in other locations
Gross Pathology
- •
Poorly circumscribed, firm, gray-white, rubbery nodule usually smaller than 3 cm
- •
Gritty cut surface
Histopathology
- •
Bland oval plump fibroblasts in a heavily collagenized stroma
- •
Foci of stippled to confluent amorphous calcifications surrounded by rounded chondrocyte-like cells ( Figure 17.9 )
Figure 17.9
Calcifying aponeurotic fibroma.
Nodular calcifications are surrounded by chondrocyte-like cells with intervening spindle cells in a hyalinized stroma.
- •
Infiltrative margins with extension into adipose tissue
- •
Osteoclast-like giant cells may be associated with calcification
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Fibromatosis (Palmar, Plantar)
- •
Characterized by fascicles of spindled uniform-appearing fibroblasts with varying amount of collagen
- •
Growth along fascial planes and tendons
- •
Absence of calcification or chondroid differentiation
- •
Usually found in adults, but plantar fibromatosis occasionally seen in children
Chondroma of Soft Tissue
- •
Typically occurs in hands of adults
- •
Characteristically a lobulated lesion composed of mature hyaline cartilage
- •
“Chondroblastoma-like” variant undergoes calcification in a diffuse pericellular rather than in a focal manner
- •
Calcifying aponeurotic fibroma is a locally aggressive lesion characterized by local recurrence (> 50% recur)
- •
Younger lesions are less heavily calcified, and older lesions show more extensive calcification and chondroid differentiation
- •
Surgical excision is the preferred treatment
Selected References
Allen P.W., Enzinger F.M.: Juvenile aponeurotic fibroma. Cancer 1970; 26: pp. 857-867.
Coffin C.M., Dehner L.P.: Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients. Pediatr Pathol 1991; 11: pp. 569-588.
Fetsch J.F., Miettinen M.: Calcifying aponeurotic fibroma: a clinicopathologic study of 22 cases arising in uncommon sites. Hum Pathol 1998; 29: pp. 1504-1510.
Fibroma of Tendon Sheath
Clinical Features
- •
Most commonly affects the hands of young to middle-aged adults; slight male predominance
- •
Presents as a slow-growing, painless mass, usually on the preaxial digits or wrist but may affect foot or knee joint
Gross Pathology
- •
Circumscribed, firm, gray-white, lobulated nodule attached to the tendon, usually smaller than 3 cm
- •
Fibrous, often multinodular cut surface separated by clefts
Histopathology
- •
Spindled to stellate cells embedded in a collagenous stroma, sometimes myxoid
- •
Clefted, pseudovascular spaces separate the nodules ( Figure 17.10 )
Figure 17.10
Fibroma of tendon sheath.
Slitlike pseudovascular spaces are present between hypocellular, collagenous nodules.
- •
Degenerative cytologic atypia may be present; giant cells are rare
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Giant Cell Tumor of Tendon Sheath
- •
Numerous giant cells, plump mononuclear cells, and variable amounts of xanthoma cells
Superficial Fibromatosis (Palmar, Plantar)
- •
Growth along fascial planes and tendons with infiltrative borders
- •
Fibroma of tendon sheath is benign and typically cured by surgical excision; recurrence is rare
Selected References
Maluf H.M., DeYoung B.R., Swanson P.E., et. al.: Fibroma and giant cell tumor of tendon sheath: a comparative histological and immunohistological study. Mod Pathol 1995; 8: pp. 155-159.
Pulitzer D.R., Martin P.C., Reed R.J.: Fibroma of tendon sheath: a clinicopathologic study of 32 cases. Am J Surg Pathol 1989; 13: pp. 472-479.
Sciot R., Samson I., van den Berghe H., et. al.: Collagenous fibroma (desmoplastic fibroblastoma): genetic link with fibroma of tendon sheath?. Mod Pathol 1999; 12: pp. 565-568.
Collagenous Fibroma
Clinical Features
- •
Also known as desmoplastic fibroblastoma
- •
Most commonly presents as slow growing painless mass in subcutaneous or deep tissues of upper extremities
- •
The majority occur in late adulthood but can occur in childhood
Gross Pathology
- •
Well-circumscribed mass, usually less than 5 cm ( Figure 17.11A )
Figure 17.11
Collagenous fibroma.
A, Gross photos showing lobulated, smooth surface with a thin fibrous pseudocapsule (left) , and cut surface showing a white, fibrous, to edematous/myxoid areas. B, Bland to mildly activated fibroblasts with elongated or stellate morphology are sparsely distributed in stroma with a predominantly lightly collagenized appearance.
- •
Cut surface gray-white with a lobulated or whorled appearance
Histopathology
- •
Hypocellular spindle to stellate cell mass embedded in a loose collagenous stroma ( Figure 17.11B )
- •
Mitotic figures are typically not seen
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Desmoid Fibromatosis
- •
Typically seen in younger patients
- •
Fascicular growth pattern with infiltrative borders that entrap connective tissues
- •
Nuclear immunoreactivity for beta-catenin usually seen
- •
Surgical resection is the standard treatment, typically does not recur
- •
May have a genetic link to fibroma of tendon sheath
Selected References
Evans H.L.: Desmoplastic fibroblastoma: a report of seven cases. Am J Surg Pathol 1995; 19: pp. 1077-1081.
Macchia G., Trombetta D., Moller E., et. al.: FOSL1 as a candidate target gene for 11q12 rearrangements in desmoplastic fibroblastoma. Lab Invest 2012; 92: pp. 735-743.
Miettinen M., Fetsch J.F.: Collagenous fibroma (desmoplastic fibroblastoma): a clinicopathologic analysis of 63 cases of a distinctive soft tissue lesion with stellate-shaped fibroblasts. Hum Pathol 1998; 29: pp. 676-682.
Nishio J., Akiho S., Iwasaki H., et. al.: Translocation t(2;11) is characteristic of collagenous fibroma (desmoplastic fibroblastoma). Cancer Genet 2011; 204: pp. 569-571.
Myofibroma/Myopericytoma and Myofibromatosis
Clinical Features
- •
Also known as infantile congenital myofibromatosis or congenital myofibromatosis in children
- •
Most common fibrous tumor of infancy
- •
About 90% occur within the first 2 years of life; however, adults may be affected
- •
Myofibroma refers to a solitary lesion (common), whereas myofibromatosis denotes multiple skin and soft tissue lesions with variable visceral involvement
- •
Solitary subcutaneous nodules typically involve the head and neck but can occur anywhere
- •
Multicentric form may involve the lungs, heart, bones, and gastrointestinal (GI) tract
- •
Gross Pathology
- •
Cut surface is rubbery gray-white with a lobulated or whorled appearance
- •
May have central necrosis or cyst formation
- •
Margins may be well defined or focally infiltrative
- •
Size from 0.5 cm up to 8 cm
Histopathology
- •
Typically shows a biphasic pattern or zonal phenomenon
- •
Peripheral areas show fascicular or whorled growth of plump, spindled cells with eosinophilic cytoplasm (myofibroblasts)
- •
Central areas of the lesion are more cellular with oval cells and a staghorn-appearing, hemangiopericytoma-like vasculature ( Figure 17.12 )
Figure 17.12
Myofibroma.
Plump, bland ovoid cells are arranged around curved, slitlike vascular channels in the central zone of this tumor.
- •
- •
Variable mitotic activity but no atypical division figures
- •
Scattered lymphoplasmacytic infiltrate typically present
- •
Polypoid protrusion into vascular spaces is typical at the edge of the lesion
- •
Focal areas of hemorrhage, calcification, and necrosis may be seen centrally
- •
May be well circumscribed or infiltrative
Special Stains and Immunohistochemistry
- •
SMA and MSA positive
- •
Desmin variable
- •
Immunohistochemistry does not help to exclude other myofibroblastic or smooth muscle proliferations
Other Techniques for Diagnosis
- •
Noncontributory aside from ruling out other selected lesions such as infantile fibrosarcoma
Differential Diagnosis
Angioleiomyoma
- •
Occurs in skin and subcutis of adults
- •
Less cellular with more complete smooth muscle differentiation
- •
Patients with solitary and multiple lesions of myofibroma or myofibromatosis confined to soft tissues have an excellent prognosis; visceral involvement imparts a worse prognosis depending on the particular locations and extent of growth
- •
Bilateral symmetric bone lesions are a radiographic clue to diagnosis in infants
- •
Lesions may spontaneously regress
- •
Surgical resection is the standard treatment
Selected References
Chung E.B., Enzinger F.M.: Infantile myofibromatosis. Cancer 1981; 48: pp. 1807-1818.
Coffin C.M., Dehner L.P.: Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients. Pediatr Pathol 1991; 11: pp. 569-588.
Daimaru Y., Hashimoto H., Enjoji M.: Myofibromatosis in adults (adult counterpart of infantile myofibromatosis). Am J Surg Pathol 1989; 13: pp. 859-865.
Zand D.J., Huff D., Everman D., et. al.: Autosomal dominant inheritance of infantile myofibromatosis. Am J Med Genet 2004; 126: pp. 261-266.
Gardner Fibroma
Clinical Features
- •
Benign lesion of childhood and early adulthood that has a strong association with desmoid-type fibromatosis and familial adenomatous polyposis (Gardner syndrome)
- •
Poorly defined, plaquelike soft tissue mass in superficial and deep tissues of back and paraspinal region, head and neck, extremities, and chest
Gross Pathology
- •
Ill-defined firm mass with a white-gray, rubbery cut surface
- •
Ranges in size from 1 to 12 cm
Histopathology
- •
Sheets of densely hyalinized bundles of collagen containing scant, small spindle cells ( Figure 17.13 )
Figure 17.13
Gardner fibroma.
This tumor of low cellularity has small, bland fibroblasts and heavy collagenization with cracks between collagen bundles. Entrapped adipocytes are present.
- •
Collagen fibers are separated by cracks or clefts
- •
Infiltrative borders are seen with entrapped connective tissue
Special Stains and Immunohistochemistry
- •
CD34 positive
- •
β-Catenin: most are positive with nuclear labeling
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Desmoid-Type Fibromatosis
- •
More cellular spindle cell proliferation with fascicular growth pattern
Nuchal Fibroma
- •
Bundles of hyalinized collagen with entrapped adnexal structures and connective tissues
- •
Frequently has proliferation of small nerves similar to traumatic neuroma
- •
Distinct clinical presentation, occurs in the posterior neck of middle-aged adults (males affected more than females); associated with diabetes mellitus in about half of cases
- •
CD34 and β-catenin stains typically negative
Elastofibroma
- •
Densely eosinophilic elastic fibers intermixed with collagen as highlighted with the Verhoeff–van Gieson elastic stain
- •
Occurs in older patients, frequently in subscapular location
- •
Not associated with familial adenomatous polyposis
- •
Gardner fibroma may be the first presentation of familial adenomatous polyposis (Gardner syndrome)
- •
About half of patients will develop desmoid-type fibromatosis
- •
Surgical resection is the standard treatment
Selected References
Allen P.W.: Nuchal-type fibroma appearance in a desmoid fibromatosis. Am J Surg Pathol 2001; 25: pp. 828-829.
Coffin C.M., Hornick J.L., Zhou H., et. al.: Gardner fibroma: a clinicopathologic and immunohistochemical analysis of 45 patients with 57 fibromas. Am J Surg Pathol 2007; 31: pp. 410-416.
Wehrli B.M., Weiss S.W., Yandow S., et. al.: Gardner-associated fibromas (GAF) in young patients: a distinct fibrous lesion that identifies unsuspected Gardner syndrome and risk for fibromatosis. Am J Surg Pathol 2001; 25: pp. 645-651.
Desmoid-Type Fibromatosis
Clinical Features
- •
Also referred to as aggressive or deep fibromatosis
- •
Relatively common neoplasm that typically occurs in adolescents and young adults, but age range is wide
- •
Comprises a group of proliferative tumors that present as deep-seated masses
- •
Shoulder region, chest wall, thigh, and mesentery are favored sites
- •
Musculoaponeurotic fibromatosis
- •
Abdominal fibromatosis
- •
Mesenteric fibromatosis
- •
Lesions are associated intimately with muscular aponeuroses
- •
Rectus muscle is the favored location
- •
Occurs almost exclusively in women who are pregnant or postpartum
- •
Found in mesentery of the bowel or retroperitoneum
- •
Often associated with previous history of abdominal surgery
- •
May be associated with Gardner syndrome (familial adenomatous polyposis, mesenteric fibromatosis, osteomas, and multiple epidermal inclusion cysts)
- •
- •
Gross Pathology
- •
May appear well defined but actually has infiltrative margins
- •
Often grows along fascial planes
- •
Firm tumor that often has a gritty cut surface
- •
Sectioning reveals a glistening, white, trabeculated surface
Histopathology
- •
Composed of uniform-appearing, spindle-shaped fibroblasts and abundant collagen ( Figure 17.14 )
Figure 17.14
Desmoid-type fibromatosis.
This area shows intermediate cellularity with bland fibroblasts and myofibroblasts in a collagenous to edematous stroma. Immunostain for β-catenin (inset) shows nuclear and cytoplasmic reactivity in many of the cells.
- •
Infiltrative margins
- •
Occasional mitotic figures are present in more cellular areas
- •
Inconspicuous vasculature
- •
Myxoid matrix may be seen, primarily in abdominal fibromatosis
Special Stains and Immunohistochemistry
- •
β-Catenin: positive nuclear immunoreactivity
- •
SMA positive
Other Techniques for Diagnosis
- •
Recurrent chromosomal abnormalities include trisomies 8 and 20 and loss of 5q, not usually needed for diagnosis; CTNNB1 gene sequencing may identify mutations with prognostic relevance.
Differential Diagnosis
Low-Grade Fibromyxoid Sarcoma
- •
Alternating collagenized and myxoid zones with prominent curvilinear vessels
- •
May contain hyaline collagen rosettes
- •
Negative for nuclear β-catenin; positive for MUC4
- •
Presence of t(7;16)(q33;p11), producing an FUS-CREB3L2 fusion in molecular or cytogenetic analysis
Fibrosarcoma (Infantile and Adult Types)
- •
Most commonly affects children younger than 1 year; occasionally seen in adults
- •
Highly cellular, infiltrative tumor composed of fibroblasts with hyperchromatic nuclei and scant cytoplasm arranged in a herringbone pattern
- •
Mitoses are obvious, and atypical mitotic figures may be seen
- •
Areas of necrosis or hemorrhage may be present
- •
Infantile fibrosarcoma harbors t(12;15)(p13;q26), producing an ETV6-NTRK fusion demonstrable by molecular or cytogenetic studies
- •
Desmoid-type fibromatosis has a high recurrence rate and may be locally aggressive but has no metastatic potential
- •
Surgical removal is controversial for most cases due to high recurrence rate
- •
Recurrence rate ranges between 25% and 80%
Selected References
Bhattacharya B., Dilworth H.P., Iacobuzio-Donahue C., et. al.: Nuclear beta-catenin expression distinguishes deep fibromatosis from other benign and malignant fibroblastic and myofibroblastic lesions. Am J Surg Pathol 2005; 29: pp. 653-659.
Carlson J.W., Fletcher C.D.: Immunohistochemistry for beta-catenin in the differential diagnosis of spindle cell lesions: analysis of a series and review of the literature. Histopathology 2007; 51: pp. 509-514.
De Wever I., Dal Cin P., Fletcher C.D., et. al.: Cytogenetic, clinical, and morphologic correlations in 78 cases of fibromatosis: a report from the CHAMP Study Group. CHromosomes And Morphology. Mod Pathol 2000; 13: pp. 1080-1085.
Calcifying Fibrous Tumor
Clinical Features
- •
Benign fibrous tumor that occurs predominantly in adolescents and young adults
- •
Most common in subcutaneous and deep soft tissues of extremities, trunk, groin, and neck but has been described in many locations, including viscera
Gross Pathology
- •
Typically a circumscribed solid mass, 3 to 5 cm, but may be larger
- •
Cut surface is solid, firm, and gray-white
Histopathology
- •
Hypocellular, sclerotic tissue with a sparse lymphoplasmacytic infiltrate and discrete calcifications ( Figure 17.15 )
Figure 17.15
Calcifying fibrous tumor.
Paucicellular, sclerotic lesion contains lymphoplasmacytic infiltrate and psammomatous calcifications.
- •
Calcification may be psammomatous or dystrophic
- •
Germinal center formation may be seen at lesion periphery
Special Stains and Immunohistochemistry
- •
Noncontributory
Other Techniques for Diagnosis
- •
Noncontributory
Differential Diagnosis
Desmoid-Type Fibromatosis
- •
Characterized by fascicles of spindle-shaped fibroblasts with varying amounts of collagen and infiltrative borders
- •
More cellular than calcifying fibrous tumor. Lacks significant calcification
- •
Positive for β-catenin nuclear reactivity in most cases
Calcifying Aponeurotic Fibroma
- •
Typically seen on hands and feet of young children
- •
Stippled calcification with surrounding chondroid differentiation
- •
Infiltrative margins
- •
Inflammation not typical
- •
Calcifying fibrous tumor is a benign lesion with rare reports of recurrence
- •
Treatment is complete surgical resection
Selected References
Hill K.A., Gonzalez-Crussi F., Chou P.M.: Calcifying fibrous pseudotumor versus inflammatory myofibroblastic tumor: a histological and immunohistochemical comparison. Mod Pathol 2001; 14: pp. 784-790.
Kirby P.A., Sato Y., Tannous R., et. al.: Calcifying fibrous pseudotumor of the myocardium. Pediatr Dev Pathol 2006; 9: pp. 384-387.
Lau S.K., Weiss L.M.: Calcifying fibrous tumor of the adrenal gland. Hum Pathol 2007; 38: pp. 656-659.
Nascimento A.F., Ruiz R., Hornick J.L., et. al.: Calcifying fibrous “pseudotumor”: clinicopathologic study of 15 cases and analysis of its relationship to inflammatory myofibroblastic tumor. Int J Surg Pathol 2002; 10: pp. 189-196.
Inflammatory Myofibroblastic Tumor
Clinical Features
- •
Previously known as inflammatory pseudotumor and plasma cell granuloma
- •
Most often occurs in children and young adults but has a wide age range
- •
Commonly seen in the lung; the most frequent extrapulmonary sites are mesentery and omentum, but it can involve any location
- •
Systemic symptoms and signs may be present, including fever, weight loss, anemia, increased erythrocyte sedimentation rate, and elevated C-reactive protein levels
Gross Pathology
- •
Typically circumscribed, but nonencapsulated; often multinodular
- •
Cut surface is solid, firm, and gray-white
Histopathology
- •
Variably cellular tumor comprised of spindle cells and mixed inflammatory cells in a myxoid or collagenized background ( Figure 17.16 )
Figure 17.16
Inflammatory myofibroblastic tumor.
Loose fascicles of plump myofibroblasts with admixed inflammatory cells are present. Immunostain for ALK1 (inset) shows membranous and cytoplasmic reactivity in this case.
- •
Some lesions contain large histiocytoid ganglion-like cells
- •
May be hypocellular and resemble scars
- •
Mitotic figures may be numerous
Special Stains and Immunohistochemistry
- •
Variably positive for smooth muscle markers
- •
ALK-1 protein present in about 40% of cases, more frequently in childhood tumors
Other Techniques for Diagnosis
- •
Rearrangement of ALK locus at 2p23 by molecular or cytogenetic analysis
Differential Diagnosis
Leiomyosarcoma
- •
Characterized by fascicles of cytologically atypical spindle cells with hyperchromatic nuclei and variable but present mitotic activity
- •
May have inflammatory infiltrate, usually patchy
- •
Typically, middle-aged and elderly adults are affected
Desmoid-Type Fibromatosis
- •
Fascicles of spindle-shaped fibroblasts with variable amounts of collagen and infiltrative borders
- •
Positive for β-catenin with nuclear labeling in most cases
- •
Lacks inflammatory infiltrate
Embryonal Rhabdomyosarcoma
- •
Primitive spindle cells, usually in a myxoid background; focal strap cells may be present
- •
Usually lacks inflammation
- •
Positive for desmin, myogenin, and MyoD1
Inflammatory Pleomorphic Undifferentiated Sarcoma
- •
Usually occurs in older adults; retroperitoneum is the most common location
- •
Cases with associated liposarcoma or MDM2 amplification are best classified as dedifferentiated liposarcoma
- •
Atypical hyperchromatic cells with prominent mixed inflammation rich in xanthomatous cells
- •
Negative for SMA and ALK-1
Metastatic Sarcomatoid Carcinoma
- •
Usually supported by clinical history or imaging, with similar histology as primary
- •
May have areas of squamous differentiation
- •
At least focally positive for keratin, EMA, MOC31, or p63
Spindle Cell Melanoma
- •
Variably cellular spindle cell lesion with variable cellular pleomorphism, prominent nucleoli, and nuclear pseudoinclusions
- •
May show perineural invasion extending beyond the tumoral component
- •
Positive for S100 protein, Sox10; rarely for tyrosinase, Melan-A, or HMB-45
- •
Inflammatory myofibroblastic tumor is a neoplastic process
- •
Treatment is based on surgical resection
- •
May recur after excision
Selected References
Coffin C.M., Dehner L.P., Meis-Kindblom J.M.: Inflammatory myofibroblastic tumor, inflammatory fibrosarcoma, and related lesions: an historical review with differential diagnostic considerations. Semin Diagn Pathol 1998; 15: pp. 102-110.
Coffin C.M., Hornick J.L., Fletcher C.D.: Inflammatory myofibroblastic tumor: comparison of clinicopathologic, histologic, and immunohistochemical features including ALK expression in atypical and aggressive cases. Am J Surg Pathol 2007; 31: pp. 509-520.
Cook J.R., Dehner L.P., Collins M.H., et. al.: Anaplastic lymphoma kinase (ALK) expression in the inflammatory myofibroblastic tumor: a comparative immunohistochemical study. Am J Surg Pathol 2001; 25: pp. 1364-1371.
Solitary Fibrous Tumor
Clinical Features
- •
Typically occurs in middle-aged adults but has a wide age range
- •
Includes cases previously called hemangiopericytoma (except nasal type)
- •
Presents as a localized, slow-growing, painless mass
- •
Most commonly involves the pleura; extrapleural sites include subcutaneous and deep soft tissues, orbit, retroperitoneum, mediastinum, pericardium, and other locations
Gross Pathology
- •
Ranges in size from 1 to 27 cm
- •
Typically well circumscribed with a firm, tan-white cut surface; sometimes multinodular
- •
Focal necrosis, hemorrhage, and cystic degeneration may be seen
Histopathology
- •
Characterized by uniform spindle cells haphazardly arranged in a collagenized background ( Figure 17.17 ); collagen focally surrounds individual cells
Figure 17.17
Solitary fibrous tumor.
Monotonous ovoid and spindle tumor cells arranged around a hyalinized vasculature.
- •
Hypercellular and hypocellular, collagenous areas (so called “patternless pattern”)
- •
“Hemangiopericytoma-like” open, staghorn-shaped, and hyalinized blood vessels
- •
Epithelioid areas may be present
- •
Low mitotic activity (<4 mitotic figures/10 high-power fields)
- •
Criteria for malignancy include dense cellularity, numerous mitotic figures, obvious cytologic atypia, necrosis, and infiltrative growth; “dedifferentiation” (transformation to high-grade sarcoma) has been reported
Special Stains and Immunohistochemistry
- •
CD34 positive in about 85% of cases, CD99 and bcl-2 positive in about 75% of cases
- •
Nuclear immunoreactivity for STAT6 in 98% of cases
- •
STAT6 staining may be lost with transformation to high grade
- •
Other Techniques for Diagnosis
- •
Genomic inversion at 12q13 leading to fusion NAB2-STAT6 in majority of cases
Differential Diagnosis
Spindle Cell-Rich (Cellular Fibrous) Zone of Atypical Lipomatous Tumor
- •
Lipomatous area may not be appreciated if incompletely sampled
- •
Shows MDM2 and CDK4 amplification/expression. Lacks STAT6 translocation, but may show STAT6 expression
Synovial Sarcoma
- •
Monophasic spindle cell or biphasic spindle cell and epithelioid tumors with high nuclear-to-cytoplasmic ratios
- •
Herringbone growth pattern is common, but areas may resemble solitary fibrous tumor (SFT)
- •
Mitotic activity is usually easily seen
- •
Intratumoral calcifications and metaplastic bone are sometimes present
- •
Immunoreactive for keratin or TLE1, EMA, CD99, and bcl-2; CD34 negative
- •
Solitary fibrous tumor can occur at any location
- •
Has “patternless pattern” of spindle cells with hemangiopericytoma-like vasculature
- •
Usually behaves in an indolent manner but may recur or metastasize even if histologically banal; borderline tumor
- •
Surgical resection is the preferred treatment
Selected References
Dagrada G.P., Spagnuolo R.D., Mauro V.: Solitary fibrous tumors: loss of chimeric protein expression and genomic instability mark dedifferentiation. Mod Pathol 2015; 28: pp. 1074-1083.
Doyle L.A., Vivero M., Fletcher C.D., et. al.: Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics. Mod Pathol 2014; 27: pp. 390-395.
Mohajeri A., Tayebwa J., Collin A., et. al.: Comprehensive genetic analysis identifies a pathognomonic NAB2/STAT6 fusion gene, nonrandom secondary genomic imbalances, and a characteristic gene expression profile in solitary fibrous tumor. Genes Chromosomes Cancer 2013; 52: pp. 873-886.
Mosquera J.M., Fletcher C.D.: Expanding the spectrum of malignant progression in solitary fibrous tumors: a study of 8 cases with a discrete anaplastic component: is this dedifferentiated SFT?. Am J Surg Pathol 2009; 33: pp. 1314-1321.
Hemosiderotic Fibrolipomatous Tumor and Myxoinflammatory Fibroblastic Sarcoma
Clinical Features
- •
Hemosiderotic fibrolipomatous tumor (HFLT; also known as hemosiderotic fibrohistiocytic lipomatous lesion ) and myxoinflammatory fibroblastic sarcoma (MIFS) are discussed together due to their clinicopathologic and molecular similarities; hybrid tumors have been reported
- •
Presents as a localized, slow-growing, infiltrative mass of the distal extremities
- •
HFLT is most common in the subcutis of the dorsum of the foot and ankle
- •
MIFS is usually on the hands and is locally infiltrative into synovium and tendons
- •
- •
Adults are affected more often than children, and HFLT is more common in women
Gross Pathology
- •
Ranges in size from 1 to 20 cm and has infiltrative borders
- •
Tan to yellow cut section but may be gelatinous or fatty; hemorrhage may be present
Histopathology
- •
HFLT is characterized by spindle cells admixed with mature adipose tissue
- •
Abundant hemosiderin-laden macrophages and scattered inflammatory cells are present in the spindle cell component ( Figure 17.18A )
Figure 17.18
Hemosiderotic fibrolipomatous tumor/myxoinflammatory fibroblastic sarcoma; a case with mixed histology from the ankle of an adult woman.
A, A fibrohistiocytic and adipocytic proliferation with abundant hemosiderin deposition is present. B, Other areas show a myxoid matrix with lipoblast-like tumor cells.
- •
- •
MIFS is heterogenous with a myxoid component containing pseudolipoblasts, neutrophils and lymphocytes, and a bland spindle cell proliferation ( Figure 17.18B )
- •
Large ganglion celllike or Reed-Sternberg–like cells with prominent nucleoli are present in MIFS
- •
Low mitotic activity (<3 mitotic figures/10 high-power fields)
- •
Special Stains and Immunohistochemistry
- •
CD34 immunoreactivity in the spindle cell component in both HFLT and MIFS
- •
SMA, desmin, and S100 are negative
Other Techniques for Diagnosis
- •
Presence of t(1;10) (p22;q24) producing a TGFBR3-MGEA5 fusion has been reported in both HFLT and MIFS (as well as pleomorphic hyalinizing angiectatic tumor)
Differential Diagnosis
Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma
- •
Presents in the retroperitoneum and deep soft tissues of proximal extremities
- •
Typically lacks prominent spindle cell component; variation in size of adipocytes and lipoblasts may be present
- •
Morphology of dedifferentiated, inflammatory areas resemble MIFS
- •
The large hyperchromatic nuclei in scattered cells of typical atypical lipomatous tumor (ALT) lack prominent nucleoli
- •
Lacks prominent hemosiderin deposition
- •
MDM2 and CDK4 amplification and expression
Inflammatory Pleomorphic Undifferentiated Sarcoma
- •
Usually occurs in older adults; retroperitoneum is the most common location
- •
Some cases best classified as dedifferentiated liposarcoma if associated liposarcoma or MDM2 amplification is found
- •
Atypical hyperchromatic cells with prominent mixed inflammation rich in xanthomatous cells
Plexiform Fibrohistiocytic Tumor
- •
Dermal/subcutaneous mass in the extremities of young adults
- •
Distinct nodules composed of mononuclear histiocytoid cells, osteoclast-like giant cells, and fibroblasts in whorls or fascicles
- •
Hemorrhage may be present
Myxofibrosarcoma
- •
Usually more proximal extremity
- •
Lacks granulation tissue-like areas with dense inflammatory cell infiltrate
- •
HFLT and MIFS are genetically linked tumors
- •
Considered benign but locally aggressive, with up to a 50% recurrence rate
- •
Metastasis is rare and more common in those with MIFS histology, and dedifferentiation of HFLT has been reported
Selected References
Antonescu C.R., Zhang L., Nielsen G.P., et. al.: Consistent t(1;10) with rearrangements of TGFBR3 and MGEA5 in both myxoinflammatory fibroblastic sarcoma and hemosiderotic fibrolipomatous tumor. Genes Chromosomes Cancer 2011; 50: pp. 757-764.
Elco C.P., Marino-Enriquez A., Abraham J.A., et. al.: Hybrid myxoinflammatory fibroblastic sarcoma/hemosiderotic fibrolipomatous tumor: report of a case providing further evidence for a pathogenetic link. Am J Surg Pathol 2010; 34: pp. 1723-1727.
Laskin W.B., Fetsch J.F., Miettinen M.: Myxoinflammatory fibroblastic sarcoma: a clinicopathologic analysis of 104 cases, with emphasis on predictors of outcome. Am J Surg Pathol 2014; 38: pp. 1-12.
Solomon D.A., Antonescu C.R., Link T.M., et. al.: Hemosiderotic fibrolipomatous tumor, not an entirely benign entity. Am J Surg Pathol 2013; 37: pp. 1627-1630.
Weiss V.L., Antonescu C.R., Alaggio R., et. al.: Myxoinflammatory fibroblastic sarcoma in children and adolescents: clinicopathologic aspects of a rare neoplasm. Pediatr Dev Pathol 2013; 16: pp. 425-431.
Wettach G.R., Boyd L.J., Lawce H.J., et. al.: Cytogenetic analysis of a hemosiderotic fibrolipomatous tumor. Cancer Genet Cytogenet 2008; 182: pp. 140-143.
Low-Grade Fibromyxoid Sarcoma
Clinical Features
- •
Also known as Evans tumor. One variant originally termed “hyalinizing spindle cell tumor with giant rosettes”
- •
Typically seen in young adults but can occur in children and elderly
- •
Deep soft tissue mass most often in proximal extremities or trunk
- •
May be present for several years before diagnosis
Gross Pathology
- •
Usually a large and nonencapsulated but well-circumscribed mass
- •
Cut surface is firm, white, or tan, sometimes with a myxoid appearance
Histopathology
- •
Bland fusiform cells with variably collagenous to myxoid stroma ( Figure 17.19 )
Figure 17.19
Low-grade fibromyxoid sarcoma.
This bland spindle cell tumor with low cellularity shows variably myxoid to collagenous stroma.
- •
Collagenized areas are arranged in short haphazard fascicles
- •
A whorling growth pattern, myxoid nodules, and a prominent arcade of hyalinized vessels may be present
- •
Rosettes may be present, characterized by hyalinized nodules cuffed by tumor cells
- •
Mitotic figures are absent or sparse
- •
May be seen as a hybrid with sclerosing epithelioid fibrosarcoma or less commonly with an undifferentiated round cell component
Special Stains and Immunohistochemistry
- •
Immunoreactive toward MUC4
- •
Variably positive for EMA, SMA, desmin, and CD34
Other Techniques for Diagnosis
- •
Presence of t(7;16)(q34;p11), producing an FUS-CREBL2 fusion, can be demonstrated by cytogenetic or molecular analysis in most cases
Differential Diagnosis
Desmoid-Type Fibromatosis
- •
May be indistinguishable on routine morphology, especially in small samples
- •
Usually shows nuclear beta-catenin
- •
Lacks MUC4 expression and FUS-CREBL2 fusion
Spindle Cell-Rich (Cellular Fibrous) Zone of Atypical Lipomatous Tumor
- •
Lipomatous area may not be appreciated if incompletely sampled
- •
Shows MDM2 amplification
Myxoma (“Cellular Variant”)
- •
Less cellular overall than low-grade fibromyxoid sarcoma (LGFMS)
- •
Less collagenous, even in most fibrous areas
- •
GNAS mutations present, as in typical myxoma
Low-Grade Myxofibrosarcoma
- •
Almost exclusively myxoid with prominent thin-walled vessels
- •
Mild cytologic atypia and pseudolipoblasts
- •
Older patients
Myxoid Neurofibroma
- •
Lacks zonation
- •
Slender, wavy nuclei with tapered ends
- •
Positive for S100 protein, CD56, and CD57
- •
Recurrence is common if incompletely excised
- •
Metastatic rate varies widely in case series reports, with average interval of 5 years, and up to 45
Selected References
Billings S.D., Giblen G., Fanburg-Smith J.C.: Superficial low-grade fibromyxoid sarcoma (Evans tumor): a clinicopathologic analysis of 19 cases with a unique observation in the pediatric population. Am J Surg Pathol 2005; 29: pp. 204-210.
Doyle L.A., Moller E., Dal Cin P., et. al.: MUC4 is a highly sensitive and specific marker for low-grade fibromyxoid sarcoma. Am J Surg Pathol 2011; 35: pp. 733-741.
Evans H.L.: Low-grade fibromyxoid sarcoma: a clinicopathologic study of 33 cases with long-term follow-up. Am J Surg Pathol 2011; 35: pp. 1450-1462.
Evans H.L.: Low-grade fibromyxoid sarcoma: a report of 12 cases. Am J Surg Pathol 1993; 17: pp. 595-600.
Guillou L., Benhattar J., Gengler C., et. al.: Translocation-positive low-grade fibromyxoid sarcoma: clinicopathologic and molecular analysis of a series expanding the morphologic spectrum and suggesting potential relationship to sclerosing epithelioid fibrosarcoma: a study from the French Sarcoma Group. Am J Surg Pathol 2007; 31: pp. 1387-1402.
Rekhi B., Deshmukh M., Jambhekar N.A.: Low-grade fibromyxoid sarcoma: a clinicopathologic study of 18 cases, including histopathologic relationship with sclerosing epithelioid fibrosarcoma in a subset of cases. Ann Diagn Pathol 2011; 15: pp. 303-311.
Low-Grade Myofibroblastic Sarcoma
Clinical Features
- •
Also known as myofibrosarcoma
- •
Distinctive low-grade tumor with myofibroblastic differentiation
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Tumor of middle-aged adults, rarely reported in children
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Most commonly involves head and neck
Gross Pathology
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Firm mass with white cut surface and poorly defined margins
Histopathology
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Moderately cellular spindle cell lesion arranged in fascicles and whorls ( Figure 17.20 )
Figure 17.20
Low-grade myofibroblastic sarcoma.
Fascicles of fibroblasts with low to moderate cellularity are present. Mild cytologic atypia is evident on higher magnification (inset) . Scattered inflammatory cells are present in this example.
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Modest nuclear hyperchromasia and mild cellular pleomorphism
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Infiltrates adjacent tissues
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Mitotic figures are variable in number
Special Stains and Immunohistochemistry
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Desmin, MSA, SMA: at least one is positive
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Desmoid-Type Fibromatosis
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Lacks cellular pleomorphism
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Positive for β-catenin with nuclear labeling in most cases
Low-Grade Fibromyxoid Sarcoma
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Hypocellular myxoid areas and collagenized foci
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Possible presence of hyalinizing rosettes
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Presence of t(7;16)(q34;p11), producing an FUS-CREBL2 fusion, is characteristic
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Wide surgical resection is necessary for low-grade myofibroblastic sarcoma
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Local recurrence is common; metastases are rare but may be seen after many years
Selected References
Cai C., Dehner L.P., El-Mofty S.K.: In myofibroblastic sarcomas of the head and neck, mitotic activity and necrosis define grade: a case study and literature review. Virchows Arch 2013; 463: pp. 827-836.
Fisher C.: Myofibrosarcoma. Virchows Arch. 2004; 445: pp. 215-223.
Gonzalez-Campora R., Escudero A.G., Rios Martin J.J., et. al.: Myofibrosarcoma (low-grade myofibroblastic sarcoma) with intracytoplasmic hyaline (fibroma-like) inclusion bodies. Ultrastruct Pathol 2003; 27: pp. 7-11.
Mentzel T., Dry S., Katenkamp D., et. al.: Low-grade myofibroblastic sarcoma: analysis of 18 cases in the spectrum of myofibroblastic tumors. Am J Surg Pathol 1998; 22: pp. 1228-1238.
Infantile Fibrosarcoma
Clinical Features
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Occurs primarily in children younger than 2 years; about 25% are congenital
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Most common on extremities, followed by trunk and head and neck
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May mimic a vascular lesion both clinically and radiographically; large “hemangiomas” in young children should undergo biopsy if they enlarge
Gross Pathology
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Infiltrative borders
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Firm, fleshy, lobulated mass, often large
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Cut surface is gray-white to tan-yellow
Histopathology
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Cellular tumor is characterized by apposed, spindle-shaped fibroblasts arranged in interlacing fascicles or a herringbone pattern ( Figure 17.21 )
Figure 17.21
Infantile fibrosarcoma.
Cellular fascicles of spindle cells are arranged in herringbone growth pattern.
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Frequent mitotic activity is seen, sometimes with atypical forms
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Necrosis and hemorrhage are common
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Myxoid or collagenous stroma may be seen
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May have focal hemangiopericytoma-like vasculature
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Scattered chronic inflammatory cells and focal extramedullary hematopoiesis are seen
Special Stains and Immunohistochemistry
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Negative for epithelial, muscle, and neural markers as well as CD34, bcl-2, and CD99
Other Techniques for Diagnosis
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Up to 90% of cases have t(12;15)(p13;q26) that creates a fusion gene, ETV6-NTRK3 ( TEL-TRCKC ): this may be cryptic on conventional karyotyping and requires reverse transcription polymerase chain reaction or fluorescent in situ hybridization studies
Differential Diagnosis
Myofibroma and Myofibromatosis
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Infantile fibrosarcoma may contain foci indistinguishable from those of myofibroma; shows more cellular and atypical areas as well
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Biphasic areas of cellular density
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Possible intravascular polypoid projections
Spindle Cell Rhabdomyosarcoma
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Usually paratesticular when seen in children
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Possible presence of strap cells
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Positive for desmin, myogenin, and MyoD1
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Wide surgical excision is the preferred treatment for infantile fibrosarcoma
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Chemotherapy is reserved for unresectable tumors
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About 15% to 30% of cases recur, but metastases are rare
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Presence of t(12;15) is also seen in cellular mesoblastic nephroma of the kidney and secretory carcinoma
Selected References
Bourgeois J.M., Knezevich S.R., Mathers J.A., et. al.: Molecular detection of the ETV6-NTRK3 gene fusion differentiates congenital fibrosarcoma from other childhood spindle cell tumors. Am J Surg Pathol 2000; 24: pp. 937-946.
Coffin C.M., Jaszcz W., O’Shea P.A., et. al.: So-called congenital-infantile fibrosarcoma: does it exist and what is it?. Pediatr Pathol 1994; 14: pp. 133-150.
Sandberg A.A., Bridge J.A.: Updates on the cytogenetics and molecular genetics of bone and soft tissue tumors: congenital (infantile) fibrosarcoma and mesoblastic nephroma. Cancer Genet Cytogenet 2002; 132: pp. 1-13.
Adult Fibrosarcoma
Clinical Features
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Rare tumor of middle-aged to elderly adults
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Located in deep tissue of extremities, trunk, or head and neck; rarely other locations
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A similar histologic pattern is seen in transformation of dermatofibrosarcoma protuberans
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May be seen as a post-irradiation neoplasm
Gross Pathology
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Firm, lobulated mass usually 3 to 10 cm in diameter
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Small tumors may be well circumscribed
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Cut surface is gray-white to tan-yellow with hemorrhage or necrosis
Histopathology
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Variably hyperchromatic spindle cells with eosinophilic or amphophilic cytoplasm, may show a herringbone growth pattern
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Variable mitotic activity
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Lacks significant pleomorphism
Special Stains and Immunohistochemistry
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Negative for epithelial, muscle, and neural markers as well as CD34, CD99, bcl-2, STAT6, and nuclear β-catenin. Preserved expression of H3K27me2
Other Techniques for Diagnosis
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Noncontributory except to rule out other tumors, especially monophasic synovial sarcoma t(X;18)
Differential Diagnosis
Desmoid-Type Fibromatosis
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Lacks dense cellularity, nuclear hyperchromasia, and herringbone growth
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No hemorrhage or necrosis
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Positive for nuclear β-catenin in most cases
Synovial Sarcoma (Monophasic)
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May have herringbone or hemangiopericytoma-like growth patterns
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Commonly shows areas of hypercellularity and hypocellularity
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Immunoreactivity for cytokeratin, EMA, TLE1, CD99, bcl-2, and CD57
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Presence of t(X;18); SYT translocation by FISH
Malignant Peripheral Nerve Sheath Tumor
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Composed of elongated cells with variably pleomorphic, wavy nuclei
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Cells arranged in fascicles or whorls; possible formation of neural tactoids
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Nuclear palisading sometimes seen
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May be positive for S100 protein, glial fibrillary acidic protein (GFAP), and CD56, or may show loss of H3K27me3 and H3K27me2
Dedifferentiated and Spindle Cell Liposarcoma
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May be seen de novo through the clonal evolution of well-differentiated liposarcoma
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Dedifferentiated areas may mimic fibrosarcoma, but extensive sampling usually reveals low-grade adipocytic component
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Most commonly occurs in the retroperitoneum
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MDM2 and CDK4 amplification and expression detected
Low-Grade Fibromyxoid Sarcoma
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Alternating hypocellular myxoid areas and collagenized spindle cell foci
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Lacks herringbone grown pattern
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Presence of t(7;16) or FUS rearrangement by FISH
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Wide resection, with or without adjuvant radiotherapy, for adult fibrosarcoma is standard therapy; chemotherapy may be indicated for high-grade tumors
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Fibrosarcoma is a pathologic diagnosis of exclusion and likely makes up less than 1% of sarcomas
Selected References
Bahrami A., Folpe A.L.: Adult-type fibrosarcoma: a reevaluation of 163 putative cases diagnosed at a single institution over a 48-year period. Am J Surg Pathol 2010; 34: pp. 1504-1513.
Hansen T., Katenkamp K., Brodhun M., et. al.: Low-grade fibrosarcoma: report on 39 not otherwise specified cases and comparison with defined low-grade fibrosarcoma types. Histopathology 2006; 49: pp. 152-160.
Pritchard D.J., Soule E.H., Taylor W.F., et. al.: Fibrosarcoma: a clinicopathologic and statistical study of 199 tumors of the soft tissues of the extremities and trunk. Cancer 1974; 33: pp. 888-897.
Sclerosing Epithelioid Fibrosarcoma
Clinical Features
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Distinctive variant of fibrosarcoma
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Tumor of middle-aged adults, but has been reported in children
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Common locations include deep soft tissue of extremities, trunk, chest wall, or head and neck; may be painful
Gross Pathology
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Firm, oval, or lobulated soft tissue mass ranging in size from 2 to 20 cm
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Cut surface is gray-white; may have myxoid or cystic areas
Histopathology
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Nests or cords of uniform, round to oval tumor cells with eosinophilic to clear cytoplasm embedded in a densely hyalinized stroma ( Figure 17.22 )
Figure 17.22
Sclerosing epithelioid fibrosarcoma.
Small epithelioid cells with nuclear atypia are set in a sclerotic matrix.
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May have fascicular, myxoid, or cystic areas and hemangiopericytoma-like vasculature
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Mitotic figures are infrequent
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Some cases have an associated low-grade fibromyxoid sarcoma
Special Stains and Immunohistochemistry
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Most cases are positive for MUC4, variably for EMA. Typically negative for cytokeratins
Other Techniques for Diagnosis
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Rearrangements in FUS have been reported in tumor with LGFMS component
Differential Diagnosis
Metastatic Carcinoma
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Histology may suggest lobular breast carcinoma or signet ring cell adenocarcinoma
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Positive for keratin, p63, MOC31, or CA72.4
Sclerosing Lymphoma
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Positive for leukocyte common antigen (CD45) and B-cell markers (CD20, CD79a, and PAX5)
Deep Fibromatosis
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Cells tend to be more fusiform, and margins are infiltrative
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Positive for nuclear β-catenin in most cases
Spindle Cell/Sclerosing Rhabdomyosarcoma
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Eosinophilic, hyperchromatic, and spindled to ovoid cells
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Positive for desmin, myogenin, and MyoD1
Sclerosing, Well-Differentiated Liposarcoma
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Usually retroperitoneal
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Usually contains lipomatous areas if well sampled
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Nuclear pleomorphism and lipoblasts are present
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Wide surgical resection is mainstay of therapy for sclerosing epithelioid fibrosarcoma
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Local recurrence in about 50% of cases; distant metastases are common
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Genetic and histologic overlap with low-grade fibromyxoid sarcoma in some cases
Selected References
Antonescu C.R., Rosenblum M.K., Pereira P., et. al.: Sclerosing epithelioid fibrosarcoma: a study of 16 cases and confirmation of a clinicopathologically distinct tumor. Am J Surg Pathol 2001; 25: pp. 699-709.
Doyle L.A., Wang W.L., Dal Cin P., et. al.: MUC4 is a sensitive and extremely useful marker for sclerosing epithelioid fibrosarcoma: association with FUS gene rearrangement. Am J Surg Pathol 2012; 36: pp. 1444-1451.
Guillou L., Benhattar J., Gengler C., et. al.: Translocation-positive low-grade fibromyxoid sarcoma: clinicopathologic and molecular analysis of a series expanding the morphologic spectrum and suggesting potential relationship to sclerosing epithelioid fibrosarcoma: a study from the French Sarcoma Group. Am J Surg Pathol 2007; 31: pp. 1387-1402.
Ogose A., Kawashima H., Umezu H., et. al.: Sclerosing epithelioid fibrosarcoma with der(10)t(10;17)(p11;q11). Cancer Genet Cytogenet 2004; 152: pp. 136-140.
Myxofibrosarcoma
Clinical Features
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Previously known as myxoid malignant fibrous histiocytoma
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Almost exclusively occurs in older adults and elderly
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Usually presents as a slow-growing, painless mass in subcutaneous or deep tissues of the proximal extremities, rarely on trunk or head and neck
Gross Pathology
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Multilobulated or single ill-defined mass with gelatinous, myxoid cut surface ( Figure 17.23A )
Figure 17.23
Myxofibrosarcoma, low grade.
A, The tumor is grossly well circumscribed with a shiny yellow-tan, soft appearance, but infiltrated to the margins microscopically, necessitating re-excision. B, On microscopic examination, tumor cells with mild to moderate atypia are present singly in abundant myxoid stroma, or apparently clinging (arrows) to the delicate thin-walled vasculature. Tumor cells with intracytoplasmic mucoid material known as “pseudo-lipoblasts” (inset) are present.
Histopathology
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Multilobulated lesion demarcated with incomplete fibrous septa containing a myxoid stroma and pleomorphic cells
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Low-grade myxofibrosarcoma
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Abundant myxoid matrix with scattered spindled or stellate hyperchromatic tumor cells with irregular borders and eosinophilic cytoplasm ( Figure 17.23B )
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Pseudolipoblasts show eccentric, pleomorphic nuclei and abundant vacuolated cytoplasm
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Curvilinear blood vessels with perivascular condensation of tumor cells
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High-grade myxofibrosarcoma
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Cellular tumor composed of fascicles or sheets of highly pleomorphic fusiform or stellate cells, many of which are multinucleated
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Lower grade areas may be present
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Myxoid stroma that is less apparent but variable throughout the lesion
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Numerous mitotic figures and atypical mitoses
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Hemorrhage and necrosis common
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Rarely, has an epithelioid phenotype
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Special Stains and Immunohistochemistry
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Noncontributory
Other Techniques for Diagnosis
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Noncontributory
Differential Diagnosis
Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma with myxoid stroma
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Fatty component is usually evident if well sampled
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MDM2/CDK4 expression and amplification
Low-Grade Fibromyxoid Sarcoma
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Much more fibroblastic, collagenous tumor, despite similarity of name
Myxoid Liposarcoma
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Deeply seated tumor that most commonly occurs in the thighs of adults
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Bland spindled or fusiform cells with presence of true lipoblasts
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Tumor cells are less pleomorphic
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Vasculature is delicate and arborizing and lacks condensed perivascular tumor cells
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Presence of t(12;16)(q13;p11), producing an FUS-DDIT3 fusion
Myxoma
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Paucicellular lesion with small, bland nuclei that lack pleomorphism
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Usually intramuscular
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Wide surgical resection with radiation, chemotherapy, or both for high-grade lesions is the standard therapy for myxofibrosarcoma
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Low-grade tumors show local recurrence in up to 50% of cases but rarely metastasize
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High-grade tumors have a high rate of local recurrence and metastasize in about one third of cases
Selected References
Mentzel T., Calonje E., Wadden C., et. al.: Myxofibrosarcoma: clinicopathologic analysis of 75 cases with emphasis on the low-grade variant. Am J Surg Pathol 1996; 20: pp. 391-405.
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