Leiomyosarcoma

 Lesions restricted to cutis only rarely metastasize






Microscopic




• Perpendicularly oriented fascicles of spindle cells

• Brightly eosinophilic cytoplasm

• Blunt-ended nuclei

• Nuclear atypia and mitoses


Ancillary Tests




• Labels as per smooth muscle: Desmin, actin, calponin, caldesmon
image Some cases stain with keratins


Top Differential Diagnoses




• Sarcomatoid squamous cell carcinoma

• Atypical fibroxanthoma

• Leiomyoma

• Dermatofibroma/fibrous histiocytoma

• Nodular fasciitis

• Inflammatory myofibroblastic tumor

image
Cutaneous Leiomyosarcoma (Atypical Smooth Muscle Tumor)
Based on the lack of involvement of the subcutaneous adipose tissue, a favorable prognosis would be anticipated for this lesion. In fact, some observers have suggested diagnosing such superficial cutaneous lesions as atypical smooth muscle tumors.


image
Superficial Area of Cutaneous Leiomyosarcoma
This leiomyosarcoma (LMS) extended into the subcutis. It is composed of perpendicularly oriented fascicles of brightly eosinophilic cells. Even at scanning magnification, atypical nuclei stand out image.

image
Leiomyosarcoma at High Magnification
Mitotic figures are usually easily found in LMS. There is no need to search for numerous mitoses, although mitotic counts assist in assigning a sarcoma grade. Note the bright pink color of the tumor cells’ cytoplasm.

image
Leiomyosarcoma With Anaphase Bridge
LMSs do not show a characteristic translocation and have chromosome instability, as indicated by the presence of anaphase bridges image, long cords of chromatin that remain as cells separate in anaphase. Note the blunt-ended nuclei image.


TERMINOLOGY


Abbreviations




• Leiomyosarcoma (LMS)


Definitions




• Malignant neoplasm composed of cells exhibiting smooth muscle differentiation


ETIOLOGY/PATHOGENESIS


Infectious Agents




• Epstein-Barr virus (EBV) smooth muscle tumors (SMT) in immunosuppressed patients

• Occasional examples are radiation associated


CLINICAL ISSUES


Epidemiology




• Incidence
image Uncommon: 10-15% of extremity sarcomas

image Most common overall sarcoma type if uterine and visceral examples are included

• Age
image Middle-aged adults

• Sex
image No gender preference overall


Presentation




• Cutaneous LMS presents as single nodule or plaque-like tumor
image May be ulcerated or show serum crusting/hemorrhage

• Deep soft tissue tumors present as mass, often asymptomatic, in extremities
image Retroperitoneum most common site

image Vena cava examples often symptomatic

• Uterine examples considered separately with unique diagnostic criteria


Treatment




• Surgical excision
image Radiation

image Chemotherapy for metastatic tumors


Prognosis




• Outcome site and stage dependent as with other sarcoma types
image Lesions restricted to cutis only rarely metastasize

– Some observers have advocated diagnosing them as atypical SMTs

image Subcutaneous lesions

– Up to 40% of tumors metastasize

– Over 30% of patients with subcutaneous tumors die of disease

image Retroperitoneum: About 80% of patients die of disease, typically with metastases

image Bone: Metastases in up to 1/2 of patients

image Vena cava: 5- and 10-yr survival 50% and 30%, respectively

image Head and neck: Over 1/2 metastasize


MICROSCOPIC


Histologic Features




• Perpendicularly oriented fascicles of spindle cells

• Cells show brightly eosinophilic cytoplasm

• Blunt-ended nuclei with nuclear atypia

• Some examples are epithelioid-appearing

• Any number of mitoses sufficient in subcutis, scrotal lesions, or deep soft tissue if nuclear atypia is present

• In vulva, some observers offered > 5 mitosis per 10 HPF as cutoff, but recurrences reported in lesions with any mitotic activity


Predominant Pattern/Injury Type




• Fascicular


Predominant Cell/Compartment Type




• Mesenchymal, smooth muscle


Variant and Special Forms




• Epithelioid leiomyosarcoma
image Literature confounded because many epithelioid gastrointestinal stromal tumors (GIST) were termed epithelioid LMS in past

image Found anywhere in body

image Distinct epithelioid morphology, but more nuclear atypia than GISTs

image Older studies reported smooth muscle actin (SMA) and muscle specific actin (MSA)-positive, desmin-negative immunophenotype, but desmin labels most lesions using modern methods

– Possible reflection of misdiagnosed GISTs

– Less sensitive desmin antibodies used in past

• Myxoid leiomyosarcoma
image Grossly gelatinous

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Leiomyosarcoma
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