Myxoinflammatory Fibroblastic Sarcoma

 Inflammatory component shows variable mixtures of lymphoplasmacytic cells, eosinophils, neutrophils, and histiocytes



• Areas with prominent myxoid change

• Scattered enlarged atypical tumor cells, some with macronucleoli
image Cells with macronucleoli resemble Reed-Sternberg cells

• Fibroblasts often vacuolated (pseudolipoblasts)

• Low mitotic rate

• Lesional cells are fibroblasts ultrastructurally




Ancillary Tests




• Variable expression of CD34, CD68, EGFR, CD163, CD117, EMA

• Negative CD15, CD30, CD45 in cells with macronucleoli

• Rearrangements of TGFBR3 &/or MGEA5 reported, but their presence in these tumors is subject of debate


Top Differential Diagnoses




• Extranodal Hodgkin disease

• Pigmented villonodular tenosynovitis

• Hemosiderotic fibrohistiocytic lipomatous lesion

• Viral infection

• Myxofibrosarcoma

• Epithelioid sarcoma

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Myxoinflammatory Fibroblastic Sarcoma: Gross Specimen
This is a gross example of a myxoinflammatory fibroblastic sarcoma (MIFS). This lesion was highly infiltrative but was clinically mistaken for pigmented villonodular tenosynovitis.


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Myxoinflammatory Fibroblastic Sarcoma, Low Magnification
This MIFS is superficial and shows a myxoinflammatory expansion of the subcutaneous fat. Such neoplasms can also be associated with tendons and have an infiltrative appearance. A prominent lymphoid infiltrate image is present throughout the neoplasm.

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Myxoinflammatory Fibroblastic Sarcoma, Low Magnification
At scanning magnification, MIFS displays a generous inflammatory background and scattered myxoid zones. Lymphoid cells are prominent at the edges of the field image.

image
Myxoinflammatory Fibroblastic Sarcoma: Atypical Mitotic Figure
Finding atypical mitoses image in these tumors is unusual for a translocation sarcoma, but rearrangements TGFBR3 &/or MGEA5 have been reported in some cases.


TERMINOLOGY


Synonyms




• Acral myxoinflammatory fibroblastic sarcoma (MIFS)

• Inflammatory myxohyaline tumor of distal extremities (with virocyte or Reed-Sternberg-like cells)


Definitions




• Low-grade fibroblastic sarcoma characterized by typical acral presentation and inflammatory background, often rich in eosinophils


CLINICAL ISSUES


Presentation




• Slow-growing infiltrative mass usually affecting distal extremities (hands and feet) of adults
image Subset of lesions presents in axial rather than acral sites

• Lesions are often present for years before patients seek medical attention

• Often clinically mistaken for pigmented villonodular tenosynovitis


Prognosis




• Recurrences are common, especially in examples with prominent atypical nuclei, but metastases are rare
image Metastases in only ~ 1% of cases


MACROSCOPIC


General Features




• Highly infiltrative

• Can involve both superficial and deep soft tissues


Size




• 1-10 cm

• Most lesions measure 3-4 cm


MICROSCOPIC


Histologic Features




• Poorly marginated tumor with fibrosis, hyalinization, myxoid stroma, and inflammatory components
image Various lesions have different proportions of each component

• Variable background of lymphoplasmacytic cells, eosinophils, neutrophils, and histiocytes

• Lesional cells are fibroblasts ultrastructurally

• Scattered enlarged atypical fibroblasts, some with macronucleoli
image Cells with macronucleoli resemble Reed-Sternberg cells

• Areas with prominent myxoid change
image Fibroblasts often vacuolated (“pseudolipoblasts”)

image These areas resemble myxofibrosarcoma (malignant fibrous histiocytoma)

• Low mitotic rate
image Low proliferative index by Ki-67

image Atypical mitoses may be encountered


ANCILLARY TESTS


Immunohistochemistry




• Variable expression of CD34, CD68, EGFR, CD163, CD117, EMA
• Negative CD15, CD30, CD45 in cells with macronucleoli

• No demonstration of various viral agents

image Cases have been tested for Epstein Barr virus and for cytomegalovirus (CMV) and herpes simplex virus (HSV)


Genetic Testing




• Rearrangements of TGFBR3 &/or MGEA5 have been reported
image Same rearrangements have been reported in hemosiderotic fibrolipomatous tumor (HFLT), pleomorphic hyalinizing angiectatic tumor

image Same rearrangements have been reported in rare tumors allegedly showing features of both HFLT and MIFS termed hybrid HFLT-MIFS

image Initially myxoinflammatory fibroblastic sarcoma was associated with t(1;10)

image Subject of controversy in literature

• Probably MIFS in fact lacks rearrangements of TGFBR3 &/or MGEA5 when strict morphologic criteria are used

• Additional studies will be needed to clarify genetics of these tumors


DIFFERENTIAL DIAGNOSIS


Extranodal Hodgkin Disease




• Patients usually have history of nodal disease

• Usually no myxoid areas

• Background mostly lymphoid cells; neutrophils not common

• Reed-Sternberg cells label with CD15 and CD30 and are lymphoid rather than fibroblastic

• Managed as per lymphomas


Pigmented Villonodular Tenosynovitis



Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Myxoinflammatory Fibroblastic Sarcoma
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