Pathogenesis of benign metastasizing leiomyoma: A review

Uterine leiomyomas are benign tumors of smooth muscle origin with protean symptomatology, and are the most common gynecological tumor in women of reproductive age. Very rarely, benign uterine leiomyomas display bizarre growth patterns with associated extrauterine benign-appearing smooth muscle tumors, similar to the smooth muscle cells found in a uterine fibroid, and are given the name benign metastasizing leiomyoma (BML). We reviewed the published literature to outline the possible etiology of benign metastasizing leiomyoma (BML), and explored the similarities between BML and endometriosis. Several observations and animal experiments support the findings that BML may evolve from lymphatic and hematological spread, coelomic metaplasia and intraperitoneal seeding. The weight of available evidence support the conclusion that the mechanism used to explain the pathogenesis of endometriosis can also be used to explain BML. However, in making a diagnosis of BML, meticulous sampling of the pathology specimen should be undertaken to exclude leiomyosarcoma, which unlike BML, has an aggressive course. It is hoped that analyses of the etiology and features of this disorder will facilitate a better understanding of its pathogenesis and treatment. Target audience: Obstetricians & Gynecologists, Family Physicians Learning objectives: After completion of this article, the reader will be able to asses the clinical characteristics of Benign Metastasizing Leiomyoma. Compare the potential pathophysiology with endometriosis and differentiate benign metastasizing Leiomyoma from Leiomyosarcoma.