Rare case of retroperitoneal mitotically active leiomyoma in a postmenopausal woman.

Leiomyomas are benign smooth muscle tumors, and retroperitoneal leiomyomas without coexisting uterine leiomyomas are extremely rare. Mitotically active leiomyomas, which are leiomyomas with increased mitotic activity, are rarely observed in postmenopausal women, except under the influence of exogenous hormones. This report presents a rare case of a retroperitoneal mitotically active leiomyoma in a postmenopausal woman.