Benign metastasizing leiomyoma is a rare entity which usually presents as multiple pulmonary nodules discovered incidentally in an asymptomatic patient. Though controversial, the pathogenesis of benign metastasizing leiomyoma is thought to involve hematogenous metastasis at the time of hysterectomy or myomectomy for uterine leiomyoma. We present a case of benign metastasizing leiomyoma diagnosed by transbronchial biopsy greater than thirty years after hysterectomy. To our knowledge, benign metastasizing leiomyoma has not been previously diagnosed by this method.
A 61-year-old female was referred to our pulmonary clinic for evaluation of reticulonodular abnormalities noted on a routine CXR. The patient complained of occasional nonproductive cough, but denied other pulmonary or constitutional symptoms. She also denied any smoking history, previous pneumonias or exposure to inhaled toxins. The patient had a history of hysterectomy with unilateral oophorectomy for uterine leiomyoma in 1971. Physical exam revealed normal vitals signs and was otherwise unremarkable. Baseline spirometry was normal. The CXR did not show evidence of lymphadenopathy or effusion. The patient refused any further invasive testing for tissue diagnosis and was followed yearly. Four years later, the patient was asymptomatic and her spirometry remained normal. A follow-up CXR showed persistent reticulonodular markings. A high resolution CT scan revealed diffuse sub-centimeter lung nodules in a random distribution. The patient agreed to a fiberoptic bronchoscopy as a diagnostic measure. Bronchoalveolar lavage and cytology samples were negative for infection or malignancy. The pathologic specimens from transbronchial biopsy revealed spindle cells that lacked evidence of mitosis or necrosis. Histologic staining indicated the cells to be immunoreactive to smooth muscle actin and the lesion was classified as a smooth muscle neoplasm consistent with benign metastasizing leiomyoma. No treatment is currently planned.
Benign metastasizing leiomyoma (BML) is an uncommon cause of pulmonary nodules, with less than 80 cases reported in the literature. BML is usually found in women 3-20 years following hysterectomy, though in our case the diagnosis was made 33 years after surgery. Patient’s with BML are usually asymptomatic or have mild respiratory symptoms. The pathogenesis of BML is somewhat controversial and development of smooth muscle lesions in situ has been postulated. However, the most commonly proposed mechanism is through hematogenous spread either by uterine extension into pelvic venous channels or from surgical trauma during hysterectomy. Radiographic findings in BML include nodular or reticulonodular abnormalities. Nodules are usually multiple and well circumscribed, with size ranging from a few millimeters to several centimeters. Pleural effusions are not present and lymphadenopathy is uncommon. To our knowledge, all previous documented cases of BML have been diagnosed by needle biopsy, VATS or open biopsy. Pathologic samples reveal spindle cells which stain for smooth muscle actin, express both estrogen and progesterone receptors and exhibit few mitotic figures or evidence of cellular polymorphism. The natural history of BML is variable with both regression and slow progression of nodules reported. Anecdotal reports have described response to treatment through hormonal manipulation by progesterone withdrawal or ovarian ablation, however, treatment is not often necessary.
Benign metastasizing leiomyoma is an unusual cause of diffuse pulmonary nodules which should be considered in females with unexplained nodules and a history of surgery for uterine leiomyoma. This diagnosis may become apparent greater than thirty years after gynecological surgery. Transbronchial biopsy can provide adequate tissue sampling for diagnosis in some cases.
D.S. Frenia, None.