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INTRODUCTION

Benign metastasizing leiomyoma (BML) is a rare disease of women. It is characterized by noninvasive, nonaggressive, well-circumscribed, single or multiple tumors composed of differentiated smooth muscle cells, localized to sites other than the uterus in patients with uterine leiomyomas1–7 and, in some cases, adnexal tumors.8 BML has been identified in lungs3 and lymph nodes9 which, in addition to uterine leiomyomas, are the most common sites involved. BMLs have also been identified in the mediastinum,10,11 retroperitoneum,12 vascular channels,13 bone,14,15 heart,16 skeletal muscle,17 spine,18 and pancreas.19 Pulmonary BML is usually asymptomatic and presents with either single or multiple lung nodules of varying sizes20 found incidentally on chest x-ray or computed tomography (CT) imaging. Occasionally, patients present with mild or severe pulmonary symptoms due to BML. Most patients with BML have undergone uterine myomectomy or hysterectomy due to leiomyomas.3,6,21,22

The first report of BML in 1939 described a 36-year-old woman who presented with dyspnea and wheezing. Chest radiograph showed multiple lung nodules. At autopsy, lymph nodes, uterus, and lungs showed nodules composed of smooth muscle cells with identical morphology,23 and the term metastasizing fibroleiomyoma of the uterus was adopted. This term was later abandoned, and the name BML was proposed because of the metastatic behavior of this disease.3

BML represents a diagnostic and therapeutic challenge because of its pathogenesis and metastatic potential.3 The diagnosis should be considered in a premenopausal woman with a history of uterine leiomyoma. Patients with BML are treated by managing estrogens, either surgically or pharmacologically.24

EPIDEMIOLOGY

Pulmonary BML is a rare disease of unclear prevalence. More than 100 cases of BML have been reported, but the number of reports has been rising steadily over the past decade as BML is increasingly recognized; only a few studies have reported more than one case.3,25,26 BMLs have been identified worldwide. There is no apparent ethnic or racial predominance, in contrast to uterine leiomyoma, which is more frequent in African-American women.27,28 Countries with reports of BML are geographically diverse6,26 and include the United States,21 Portugal,29 Brazil,30 China,31 India,18 South Korea,17 Japan,32 and Turkey.9 BML is found primarily in premenopausal women who have undergone surgical procedures for treatment of uterine leiomyomas;3,6,33 however, there are cases of lung BML in women with no history of these surgeries.21 The majority of BML cases were reported in premenopausal women. Reports of BML in men and children34 have been exceedingly rare.

CLINICAL PRESENTATION

BML lung nodules have been detected in women from a few months to greater than 30 years after they have ...

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