INTRODUCTION: Benign metastasizing leiomyoma (BML) is a rare clinical entity first described in 1939 by PE Steiner as “a tumor composed histologically, in both the primary growth and its metastasis, of benign appearing, fully differentiated smooth muscle cells and dense connective tissue”. The term benign metastasizing leimyoma was later coined by JP Horstman to distinguish the myometrial origin of the disease. Since its initial description, approximately 75 cases have been reported in the medical literature. Here, we report a case of BML in a pre-menopausal, 42 year-old woman who presented with an abnormal chest radiograph.
CASE PRESENTATION: A 42 year-old African-American woman was evaluated for an abnormal chest radiograph. She denied cough, fever, chills, night sweats, weight loss, fatigue or limited exercise. Her past medical history was significant for large uterine fibroids, positive PPD and two prior D&Cs. She has never smoked or been exposed to chemicals or dusts and has lived in Queens for 30 years. She has no known allergies and takes ibuprofen prn. On exam she appeared well and vital signs were normal. Exam was normal except for a palpable, non-tender pelvic mass. ESR was elevated. PFTs revealed mild restriction and normal diffusion. The patient's chest radiograph and subsequent CT demonstrated innumerable tiny nodules in bilateral lung fields. Bronchoscopy with transbronchial biopsy was non-diagnostic. The patient underwent VATS lung biopsy with pathologic findings of benign metastasizing leiomyoma (BML). Stains for smooth-muscle actin, estrogen and progesterone receptors were positive. The patient underwent a trial of GnRH analog and responded well with significant improvement in her symptoms as well as objective improvement of her radiographic findings on CT. Subsequently, the patient elected to have a total hysterectomy with bilateral salpingoopherectomy which confirmed the absence of malignant cells.
DISCUSSIONS: BML is a rare disorder reported in women ages 23–64 with a history of fibroids. It typically presents after myomectomy by incidental findings on chest x-ray. Patients are generally asymptomatic and PFTs are normal or restrictive. The clinical course ranges from chronically-indolent to rapidly-progressive depending on hormonal status. BML in menopausal or pregnant women tends to be slowly-progressive and may even resolve. Pre-menopausal women are more likely to have progressive pulmonary insufficiency due to expanding nodules. Radiographically, BML presents as multiple, bilateral pulmonary nodules. Other patterns reported include unilateral nodules, miliary and cystic. The nodules are well circumscribed and non-calcified. Sites of metastasis include the lung, pelvic and retroperitoneal lymph nodes, omentum and muscle. The mechanism of metastasis is not well understood, but is presumed hematogenous. Histological stains for smooth-muscle actin, estrogen and progesterone receptors demonstrate the uterine smooth-muscle origin of the cells. The primary treatment for patients with BML has been TAH-BSO. The role for hormonal treatment has yet to be determined.
CONCLUSION: The pathogenesis of BML is not clearly understood. Some authors believe that it may represent a low-grade leiomyosarcoma. Also, because this disease entity is so rare, there is no established standard of care. For these reasons, identification and close follow-up of these patients is neccessary.
DISCLOSURE: Kaye Hale, No Financial Disclosure Information; No Product/Research Disclosure Information