[Benign Metastasizing Leiomyoma of the Lung;Report of a Case].

A 71-year-old woman, in whom computed tomography revealed a solitary mass shadow at the base of the left lung, underwent resection of the mass. Histopathological examination showed estrogen receptor-positive leiomyoma cells growing in cords and mixed with glandular structures composed of alveolar cells. These findings led to a diagnosis of benign metastatic leiomyoma. Benign metastatic leiomyoma is a rare disease in which histologically benign uterine leiomyoma cells metastasize to different sites of the body. However, in this patient, the presence of uterine myoma was not confirmed in the past or at present. She had a history of cervical conization, which suggests that a small amount of the leiomyoma component contained in cervical tissue may have been forced into blood vessels during surgical manipulation, causing lung metastasis.