Epithelioid leiomyoma of the oral mucosa.

Oral leiomyomas are rare because of the paucity of smooth muscle in the mouth. The solid and vascular types are the most frequent variants. The purpose of this article is to present the pathologic features and differential diagnosis of an example of epithelioid leiomyoma. A 50-year-old woman presented with a small raised nonpainful polypoid lesion of unknown duration on the right buccal mucosa. The tumor was well demarcated and consisted of large epithelioid cells with distinct cytoplasmic borders, round to oval nuclei, and prominent nucleoli. A few mitoses (4 in 20 high power fields) were present. Scattered spindle cells were also seen. The cytoplasm was eosinophilic to amphophilic and showed frequent clearing and retraction. Small capillaries were identified and surrounded by neoplastic cells that gave the lesion an angiomyomatous appearance. Masson trichrome stain highlighted focally smooth muscle cells. Immunohistochemical evaluation revealed staining for vimentin, desmin, and muscle-specific actim.