Benign metastasizing leiomyoma: 'a sheep in wolf's clothing'

Benign metastasizing leiomyoma (BML) is a rare entity, of which a small number of cases, about 75 to 120, have been described in the literature since the condition was first described in 1939. It usually affects women of reproductive age with a history of uterine leiomyomatosis who have undergone a hysterectomy. The lung is the most common site of involvement. The pathologic features of this entity are described as having originated from the metastasis of the histologically benign uterine leiomyoma and are an uncommon lesion characterized by the presence of multiple smooth-muscle nodules that are often located in the lung, lymph nodes, or abdomen. Although these lesions are slow growing and asymptomatic and are usually incidentally diagnosed, they may rarely cause debilitating symptoms. Optimal treatment is controversial, but careful follow-up of these patients is recommended because the lesions show a lowgrade clinical malignant behavior although their appearance is benign. We describe here a rare case of pulmonary BML.