[A case of so-called benign metastasizing leiomyoma]

A 44-year-old female was admitted to our hospital for the purpose of undergoing hysterectomy for removal of multiple uterine tumors. A chest X-ray film obtained on admission revealed a solitary nodule in the right lung field. The resected specimen containing the uterine tumors revealed well differentiated leiomyoma with no nuclear atypia or mitotic figures. The resected specimen from the pulmonary tumor revealed histologic findings similar to those of the uterine myomas, being devoid of any signs of mitosis. Similar cases have been reported as so-called benign metastasizing leiomyoma, and are generally regarded as low grade malignancy or leiomyomatosis. However, we consider this case to have had a primary pulmonary leiomyoma associated with uterine myoma since the pulmonary lesion was solitary and no mitotic figures were detectable. As the concept of metastasizing leiomyoma is confusing, the accumulation of additional case reports is necessary.