Myoepithelioma of the vulva.

Abstract

The histologic diagnosis of myoepithelioma is often problematic. We here describe a case of myoepithelioma, composed exclusively of neoplastic myoepithelial cells, in the vulva of a 52-year-old female. The vulva is a very rare site for this neoplasm. A subcutaneous tumor measuring 3.0 x 2.5 x 2.0 cm displayed a multinodular growth pattern. Histologically, it was characterized by epithelioid, trabecular, cord, solid, or reticular arrangements of tumor cells and markedly hyalinized stroma. The tumor cells were large and polygonal with eccentrically located round to oval nuclei with prominent nucleoli and eosinophilic cytoplasm. Some cells had clear cytoplasm. Moderate cellular atypia was seen and there were 4 mitotic figures per 10 high-power fields. No ductal architecture was found and there were no areas of chondroid or osseous differentiation. There was no destructive invasive growth. Immunohistochemically the tumor was positive for vimentin, epithelial membrane antigen, wide keratin, alpha-smooth muscle actin, S-100 protein, and glial fibrillary acidic protein. The patient was well and free of disease at 6 months. This neoplasm should be distinguished from other epithelial and mesenchymal neoplasms as it shows a different clinical behavior.