Clear-cell epithelioid leiomyoma of the round ligament

A case of clear-cell epithelioid leiomyoma of the round ligament in a 69-year-old woman is described. The neoplasm presented as a firm left inguinal mass. A preoperative computed tomography (CT) scan demonstrated an enhancing lesion extending extra-abdominally from the region of the external inguinal ring. The surgical resection specimen was tan-white, well-circumscribed, and measured 5.8 cm in maximum dimension. Microscopic examination revealed a well-demarcated neoplasm comprised of polygonal cells with abundant clear cytoplasm arranged in clusters and single files with abundant intervening hyalinized stroma. There was minimal nuclear atypia and mitotic figures were rare. Periodic acid-Schiff with diastase demonstrated intracytoplasmic glycogen. Immunohistochemical stains for pan-actin, smooth muscle actin, desmin, bcl-2, and vimentin were positive in the tumor cells, whereas stains for CD34, carcinoembryonic antigen, cytokeratin, epithelial membrane antigen, S100 protein, and neurofilaments were negative. Electron microscopy demonstrated features of smooth muscle differentiation including longitudinally oriented fine filaments with focal condensations, pinocytotic activity, and subplasmalemmal densities. This case illustrates the ubiquitous distribution of epithelioid smooth muscle neoplasms and highlights the potential pitfalls for diagnosis when they occur in an unusual location.