INTRODUCTION: Benign metastasizing leiomyoma (BML) is a very rare disorder thought to result from hematogenous spread of a uterine leiomyoma. The lung is the most commonly reported site of metastasis and solitary as well as multiple pulmonary nodules or masses have been reported. Most cases in the literature appear to follow surgical manipulation of a leiomyomatous uterus. We report the case of a woman with benign metastatic leiomyoma to the lung without prior uterine surgery.
CASE PRESENTATION: A 44-year old morbidly obese female with chronic exertional dyspnea was found to have a 1.5 centimeter solitary pulmonary nodule in the right lung. She was a lifetime non-smoker and gave no history of pneumonia or other pulmonary disease. A PPD skin test and serological evaluation for endemic fungal infections were negative. Although she was premenopausal and had a history of heavy menses, she was not known to have fibroids or other uterine pathology. Breast examination and mammography were negative. A fluorodeoxyglucose (FDG) positron emission tomography showed no FDG uptake of the lesion. Given her relatively low risk for malignancy surveillance imaging was recommended; however there appeared to be slight interval enlargement over 6-9 months. The patient subsequently underwent a right chest video-assisted thoracoscopic surgery (VATS) with right lower lobe wedge resection. Histologic evaluation of the lung nodule showed a spindle cell tumor strongly positive for both estrogen and progesterone receptors. Glandular tissue embedded in the tumor was TTF-1 positive and thought to represent pulmonary epithelial entrapment vice a biphasic neoplasm. The tumor was also CD10 positive and showed unambiguous evidence of smooth muscle differentiation by immunohistochemistry analysis (muscle specific actin, myosin, and desmin positive). These features supported a diagnosis of a benign metastasizing leiomyoma. A pelvic ultrasound subsequently showed a leiomyomatous uterus.
DISCUSSIONS: BML is the term used by Steiner in 1939 to describe the appearance of benign smooth muscle tumors in an organ distant from the uterus. The lung is the most common site of metastasis, although other reported locations include various lymph nodes, heart, skull, spine and retroperitoneum. Most of the cases (less than 100 reported in the literature) affected middle-aged women still in their reproductive years and many of these women had previous surgical manipulation of the uterus, e.g. dilation and curettage, myomectomy, or hysterectomy for uterine leiomyomas, although in many cases the surgery was remote at the time the aberrantly discovered smooth muscle tumor was discovered. The natural history of these tumors may be benign although some may cause local compressive symptoms or metastasize further. Because most BML stain positive for estrogen and progesterone receptors they may be hormone responsive; regression following menopause or with hormone suppression has been reported.
CONCLUSION: Benign metastasizing leiomyoma is a rare entity that may present in the lung as a solitary nodule, mass or multiple nodules. The diagnosis should be considered in women of reproductive age, especially if there is a history of leiomyoma and prior surgical manipulation of the uterus. A pelvic ultrasound should be considered in the workup of middle age women with pulmonary nodules.
DISCLOSURE: Thuy Lin, No Financial Disclosure Information; No Product/Research Disclosure Information