Clinical benefit of endocrine therapy for benign metastasizing leiomyoma

Benign metastasizing leiomyoma (BML) is a rare disease that is caused by metastasis of a histologically benign leiomyoma that spreads to distant organs. Metastasis commonly follows surgical treatment of myomectomy or hysterectomy for benign uterine leiomyoma. Since the work of Steiner in 1939, several other studies have been published, but a unified view has not emerged regarding the biological nature, pathogenesis, and prognosis of this disease. In particular, a standard treatment has not been established. Here we report a case of BML of the lung and peritoneum in a premenopausal 45-year-old woman who underwent hysterectomy for uterine leiomyoma 10 years earlier. A computed tomography (CT) scan showed multiple pulmonary nodules (maximum size 48 mm) and a solitary intra-peritoneal nodule. The lung nodules were diagnosed as BML following a CT-guided needle biopsy. Histologically, the biopsied tumor was composed of spindle cells without significant atypia, and mitosis was not observed. Immunohistochemically, the tumor cells were strongly positive for smooth muscle actin, desmin, and estrogen receptor, suggesting a uterine leiomyomatous lineage. The patient was treated with a gonadotropin-releasing hormone agonist for 36 months, during which time the nodules reduced in size slightly. No new lesions appeared, and the tumors were stable at 15 months after the cessation of treatment. In conclusion, endocrine therapy can serve as one of the conservative treatments for premenopausal women with BML, rather than surgery.