The authors report a rare case of leiomyomatosis of the lung diagnosed in a 43-year-old woman, with uterine intravenous leiomyomatosis. Benign metastasizing leiomyoma (BML) is an extremely rare lesion characterized by usually multiple, benign-appearing smooth muscle tumors of the lung in females with coexisting uterine leiomyoma. On the basis of their histological and immunohistological features, a unified histogenetic view of leiomyomas with vascular invasion (LWVI) and BML of the uterus is proposed. LWVI and BML may be the same pathological entity and microscopic vascular invasion may represent the metastatic mechanism of BML. LWVI seems to be the precursor of BML.