Plexiform leiomyoma of the uterus in a patient with breast carcinoma: case report and review of the literature.

Plexiform leiomyomas of the uterus are incidental findings in hysterectomy specimens. Histogenetically, these rare tumors are classified as a variant of epithelioid leiomyomas. Most of the plexiform leiomyomas reported range in size from microscopically small lesions to less than 1 cm in largest diameter, and they macroscopically present as a nodular white-yellowish cut surface. Microscopically, the "Indian-file" pattern of epithelial-like tumor cells of plexiform leiomyomas may be confused with metastatic breast carcinoma, in particular lobular breast carcinoma, i.e.; one of the most frequent extragenital neoplasms metastasizing to the uterus. This report describes the occurrence of a large plexiform leiomyoma in a patient with a history of breast carcinoma, and draws attention to the histological differential diagnosis between these lesions. The results of immunohistochemical stainings for cytokeratin and smooth muscle actin confirmed the final diagnosis of plexiform leiomyoma.