Myoepitheliomas of the skin and soft tissues

Abstract

We describe 12 cutaneous and soft tissue myoepitheliomas, most of them in elderly patients. Morphologically the cutaneous and soft tissue myoepitheliomas revealed the same spectrum as their salivary gland counterparts. They were composed of a mixture of spindle, epithelioid and clear myoepithelial cells. Immunohistochemically they were positive to keratins and S-100 protein and reacted inconsistently with antibodies to smooth muscle actin. Morphologically they lacked any folliculo-sebaceous or apocrine differentiation. We believe that they are related to the eccrine type of cutaneous mixed tumours. Most cases had a benign behaviour, but 1 tumour metastasized, and the patient died of the tumour. Myoepitheliomas of soft tissues should be distinguished from other neoplasms with epithelial differentiation and from ossifying fibromyxoid tumour of soft parts, parachordoma and extraskeletal myxoid chondrosarcoma.

EWSR1 gene rearrangement occurs in a subset of cutaneous myoepithelial tumors: a study of 18 cases

“…4,8 Earlier studies suggested that cutaneous myoepitheliomas and their soft tissue counterparts represent points along a clinicopathological spectrum that was apparently extended to include myoepithelial tumors of the bone and of some visceral sites (lung). 1,2,5,10 Although this entity, in the above described localizations, is well established by now, the protean morphological and immunohistochemical range is still hampering the histopathological diagnosis, and the true frequency of these neoplasms is unclear until today.…”

“…All these observations are well-reported earlier. [1][2][3][4]6 The occurrence of EWSR1 rearrangement in mixed tumors, myoepitheliomas and rare myoepithelial carcinomas emphasizes that these lesions belong to a spectrum of cutaneous myoepithelial neoplasms. …”

“…[27][28][29] Metaplastic bone formation known in soft tissue myoepithelial tumors is not described in skin lesions. [1][2][3][4][5][6][7][8] Moreover, the intratumoral cytological and architectural heterogeneity of myoepithelial tumors is not a feature of ossifying fibromyxoid tumors in which uniform round to oval cells in cords and nests set in a myxohyaline stroma. 4,6,7 Immunohistochemical stains in this setting are of limited value because of the overlap with positivity for S100, GFAP, myogenic markers and rarely also keratins.…”

“…Although mixed tumors are not uncommon, purely myoepithelial tumors are very rare and only few and small series have been reported. [1][2][3][4] The presence of preexisting myoepithelial cells in the skin and viscera (eg, salivary glands, breast and lung) renders probably a pathogenetic difference with myoepithelial tumors of the soft tissue in which a normal counterpart does not exist.…”

“…[1][2][3][4][5][6] Although criteria for malignancy in myoepithelial tumors of soft tissue have been established by moderate to severe nuclear atypia, the minimal criteria for malignancy among myoepithelial neoplasms of the skin remain uncertain. 4,6,7 Hornick and Fletcher 4 reported that increased mitotic activity (up to 6 mitoses/10 HPF) among cytologically benign cutaneous myoepitheliomas might predict recurrence and metastases.…”