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myoepithelial tumor

Thursday 31 January 2008

Definition: The myoepithelial tumors have been first described in the salivary glands. Then, they have been recognized in the breast, upper aerodigestive tract and skin, and can arise primarily in soft tissue, albeit infrequently.

Myoepithelial neoplasms can occurr primarily in soft tissue (at sites otherwise entirely devoid of myoepithelial cells under normal circumstances, further underlining the non-viability of a histogenetic approach to soft tissue neoplasia).

These tumours show the same morphological spectrum as their salivary gland counterparts, occur most often in adults but also in children, show a predilection for subcutaneous or deeper soft tissue of the limbs and, in most cases, behave in a benign fashion. A

subset of these lesions show overt cytological atypia or features of malignancy and are associated with a metastasizing clinical course. Approximately 15% of cases show ductal differentiation (mixed tumours).

The subset of tumours in this category which are dominated by large pale-staining vacuolated cells have often been known as parachordoma.

Salivary myoepithelial tumors

Myoepithelial tumors are well recognized in the salivary gland, where they include salivary benign mixed tumors and salivary myoepitheliomas, which are distinguished by the degree or presence of ductal differentiation, and myoepithelial carcinomas.

Myoepithelial carcinomas comprise less than 2% of all salivary gland carcinomas and occur at a mean age of 55.

Although approximately half of salivary gland myoepithelial carcinomas arise in association with a benign mixed tumor or myoepithelioma,

Primary myoepithelial tumors of soft tissue

Like their counterpart in the salivary glands, primary myoepithelial tumors of soft tissue often have a multinodular architecture and are composed of epithelioid, clear, spindle, and/or plasmacytoid cells, frequently arranged in cords or trabeculae in a myxoid or hyalinized stroma.

The cytologic heterogeneity of these tumors is a characteristic feature: the majority of our cases (93%) were composed of more than one myoepithelial cell type, similar to prior studies.

A much higher proportion of myoepithelial tumors in soft tissue could be malignant than those in the salivary gland.

Overall, 46% of the cases in a series were classified as malignant, and interestingly, those arising in children were more likely to be malignant than those in adults (62% vs. 42%, P=0.01). (18043035)

Although approximately half of salivary gland myoepithelial carcinomas arise in association with a benign mixed tumor or myoepithelioma, this finding is rare in myoepithelial carcinomas of soft tissue: a benign precursor was identified in only 2 of the 40 malignant cases (5%) in Hornick and Fletcher’s series and in 2 of our 29 cases (7%). (18043035)

See also

- myoepithelial carcinoma of the soft tissue

Paywall References

- Thoracic Myoepithelial Tumors: A Pathologic and Molecular Study of 8 Cases With Review of the Literature. Leduc C, Zhang L, Öz B, Luo J, Fukuoka J, Antonescu CR, Travis WD. Am J Surg Pathol. 2016 Feb;40(2):212-23. doi : 10.1097/PAS.0000000000000560 PMID: 26645726

- 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