Temporary regression of a resected pulmonary benign metastasizing leiomyoma

A 55-year-old woman was referred to our department because of shadows noted on a radiograph. Computed tomography revealed shadows of circular, uniform nodules of 100-, 5-, and 8-mm diameters and clear borders in the left apical, left posterior basal, and right posterior basal segments of the inferior pulmonary lobe, respectively. All tumors had regressed slightly at the 3-month follow-up, but the tumor in the apical segment of the inferior lobe had enlarged 2 years later, and positron emission tomography showed faint accumulation. Since malignancy could not be ruled out, the tumor underwent thoracoscopic wedge resection. The histological features of the tumor resembled those of a uterine myoma that had been resected 17 years earlier. Therefore, we diagnosed the tumor as a pulmonary benign metastasizing leiomyoma. As this was a rare tumor that had initially regressed, possibly a characteristic of this type of leiomyoma, we report this case and review the available literature.