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myoepithelial carcinoma of soft tissue

Thursday 31 January 2008

Definition: 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

Molecular biology

- EWSR1-KLF15 fusion gene in :

  • renal Myoepithelial carcinoma

Paywall references

- Expanding the Spectrum of Renal Tumors in Children: Primary Renal Myoepithelial Carcinomas With a Novel EWSR1-KLF15 Fusion. Cajaiba MM, Jennings LJ, Rohan SM, Leuer KM, Anagnost MR, Fahner JB, Fulton BK, Geller JI, Perlman EJ. Am J Surg Pathol. 2016 Mar;40(3):386-94. doi : 10.1097/PAS.0000000000000545
PMID: 26523541

- 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