Benign Metastasizing Leiomyoma of the Lung

A 44-year-old woman was found to have an abnormal shadow on a chest X-ray during a regular health checkup, and visited our department. Chest computed tomography showed multiple nodular shadows in both lungs. The patient had no history of neoplasm except for myomectomy for uterine leiomyoma 6 years previously. Eighteen months later, the nodules showed a gradual increase in size, and video-assisted thoracoscopic biopsy of a nodule was performed. Histopathologically, the pulmonary nodule was composed of benign smooth muscle cells proliferating in fascicles, consistent with the diagnosis of benign metastasizing leiomyoma. Benign metastasizing leiomyoma is defined as a histologically benign uterine smooth muscle tumor that acts in a somewhat malignant fashion and produces benign metastases. Although it is a rare condition, it should be considered in asymptomatic women of reproductive age with a history of uterine leiomyoma, who present with solitary or multiple pulmonary nodules. Herein, we report a case of pulmonary benign metastasizing leiomyoma.