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myoepithelial carcinoma of soft tissue
Thursday 31 January 2008
Primary myoepithelial tumors of soft tissue are uncommon, and criteria for malignancy among these neoplasms have only recently been established.
Despite the relative rarity of carcinomas in the pediatric population, myoepithelial carcinoma seems to be disproportionately common among children and often has an aggressive clinical course.
Synopsis (18043035)
sex ratio: 1/1
age at diagnosis: newborn to 17 years (median, 9 y).
Sites: extremities, trunk, viscera (mediastinal, retroperitoneal, intracardiac), head/neck
multinodular architecture
lobular architecture
heterogeneous tumors
- tumoral epithelioid cells (93%)
- tumoral clear cells
- tumoral spindle cells
- tumoral plasmacytoid cells
- tumoral unidfferentiated round cells
tumoral cells forming nests, cords or solid sheets in a myxoid or hyalinized stroma
tumor cells focally had scant cytoplasm with round cell morphology (34%)
mitotic rate: from < 1 to 68 per 10 high power fields (median, 8)
tumor necrosis
+/- cartilaginous differentiation
+/- osseous differentiation
Immunochemistry (18043035)
cytokeratin CAM5.2 (94%)
cytokeratin AE1/AE3 (75%)
cytokeratin PAN-K (67%)]
EMA (66%).
S100 (72%)
GFAP (54%)
loss of INI/SNF5 (SMARCB1) expression (41%)
Cytogenetics
anomalies of chromosome 22
anomalies of chromosome 3p
Prognosis (18043035)
local recurrences
- 53% of recurrence afetr complete excision with negative margins
52% of metastases
43% of death (median interval of 9 months after diagnosis)
Differential diagnosis
high-grade extraskeletal myxoid chondrosarcoma
epithelioid MPNST
poorly differentiated synovial sarcoma
epithelioid sarcoma
undifferentiated carcinoma
Ewing sarcoma/pPNET (EFTs Ewing family tumors)
extrarenal maligant rhabdoid tumor (TRM)
Histogenesis
As with the majority of soft tissue neoplasms, the histogenesis of myoepithelial tumors arising in soft tissue locations is poorly understood and essentially unknown, but likely reflects a pattern of gene expression during oncogenesis rather than origin from a specific cell lineage. (18043035)
Perhaps due to their morphologic and immunophenotypic heterogeneity, these tumors are poorly but increasingly recognized and may be mistaken for a variety of other soft tissue tumors when arising outside of the salivary glands. (18043035)
In contrast to their salivary gland counterparts, myoepithelial carcinomas of soft tissue are distinguished from benign myoepitheliomas on the basis of cytologic rather than architectural features and are only infrequently associated with a preexisting benign tumor. (18043035)
Molecular biology
Loss of expression of the SMARCB1 (INI1/BAF47/SNF5) tumor-suppressor protein, originally identified in pediatric malignant rhabdoid tumors, has been noted in myoepithelial carcinomas. (25651469)
See also
myoepithelial carcinomas
SMARCB1
References
SMARCB1-deficient Vulvar Neoplasms: A Clinicopathologic, Immunohistochemical, and Molecular Genetic Study of 14 Cases. Folpe AL, Schoolmeester JK, McCluggage WG, Sullivan LM, Castagna K, Ahrens WA, Oliva E, Biegel JA, Nielsen GP. Am J Surg Pathol. 2015 Feb 3. PMID: 25651469
Gleason BC, Fletcher CD. Myoepithelial carcinoma of soft tissue in children: an aggressive neoplasm analyzed in a series of 29 cases. Am J Surg Pathol. 2007 Dec;31(12):1813-24. PMID: 18043035
