Multiple smooth muscle tumors arising in deep soft tissue of lower limbs with uterine leiomyomas.

A 40-year-old woman had multiple smooth muscle tumors in the left inguinal region, the bilateral thighs, the omentum, the peritoneum, and the right infundibulum pelvic ligament associated with uterine leiomyomas. She had a history of uterine leiomyomas, which were resected 13 years ago. Histopathologic evaluation revealed tumor masses composed of smooth muscle cells with relatively low cellularity, which were consistent with a diagnosis of leiomyoma. Tumor necrosis and nuclear atypia were absent. Mitotic figures were very scarce (less than 1 mitotic figure per 10 high-power fields). Immunohistochemical evaluation revealed a positive reaction of the tumor cells to muscle markers, estrogen receptors, and progesterone receptors. No pulmonary lesion was found. Similar instances of uterine leiomyomas with histologically benign extrauterine smooth muscle tumors have been reported. This curious condition has been referred to as "benign metastasizing leiomyoma," in which most of the reported cases involve the lungs. The distribution of extrauterine tumors in our case is very unusual and may be the first case with multiple leiomyomas in deep soft tissue of the limbs. Consideration was given to the concept that these may be of multifocal origin, rather than metastases.