Benign metastasizing leiomyoma of the lung: a case report.

Benign metastasizing leiomyoma (BML) refers to benign pulmonary neoplasm associated with a previous or coincident history of uterine leiomyomata. We report the case of a 56-year-old postmenopausal woman with a 4-year history of multiple benign leiomyomatous lesions in bilateral lungs and the uterus. The tumor cells from the lungs and uterus were focally immunoreactive for HMB-45 antibody and progesterone receptor. Immunoreactivity to HMB-45 is well known in smooth muscle cells of hamartomatous neoplasms, such as angiomyolipoma and lymphangioleiomyomatosis, but has not been reported in BML previously. These features suggest a multifocal hamartomatous histogenesis rather than metastasis in the present case.