Cutaneous myoepithelioma

Rare (mixed) tumor consisting of "myoepithelial" cells which is characterized by a large histological diversity (like the more frequent myoeptiheliomas in deep soft tissues).

Broad age spectrum at first manifestation (1st - 74th year; average: 39 years); m:w=7:3

Extremities (most often arms), head and neck region, trunk; m:w=7:3

0.3-2.7 cm large, broad-based or also polypose, sharply defined, papular or nodular, surface-smooth neoplasms.

In the most common synzitial form, there are map-like, corresponding solid tumor stalks of spidery, epitheloid or plasmocytoid, EMA (cytokeratin negative), S-100 protein positive tumor cells; moderate cell and nuclear polymorphism (numerous mitoses and tumor parenchyma necroses indicate a malignant myopetihelioma). The enclosed stroma may be myxoid or hyaline. Frequently, an EWSR1 translocation with different fusion partners (POU5F1, PBK1, ZNF444, FUS). A PLAG1-translocation (found in various adenomas) is rarer. Furthermore, myoepitheliomas with trabecular or reticular growth pattern are found. Ductal differentiations are very rare.

The tumours tend to recur more frequently at local level. The best prognosis is ascribed to synzytial myoepitheliomas. It is important to distinguish them from malignant cutaneous myoepitheliomas, as these are considered to have a high potential for metastasis.

1. Antonescu CR et al (2013) Frequent PLAG1 gene rearrangements in skin and soft tissue myoepithelioma with ductal differentiation. Genes Chromosomes Cancer 52: 675-682.
2. Dix BT et al (2012) Cutaneous myoepithelioma in the foot: case report. Foot Ankle Spec 6:239-241.
3. Jakate K et al (2012) Cutaneous myoepithelioma arising within hidradenoma of the scalp. J Cutan Pathol 39:279-285.
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5. Jo VY (2015) Myoepithelial tumors: An Update. Surg Pathol Clin 8:4445-66.
6. Lee JH et al (2015) Cutaneous syncytial myoepithelioma: A case report with emphasis on the differential diagnosis of problematic dermal tumors. Oncol Lett 9: 2275-2277.
7. Luzar B et al (2013) Paranuclear dot-like cytokeratin MNF116 positivity in cutaneous myoepithelioma. J Cutan pathogen 40: 982-984.
8. Naujokas A et al (2014) SOX-10 expression in cutaneous myoepitheliomas and mixed tumors. J Cutan Pathol 41:353-363.