Pulmonary Benign Metastasizing Leiomyoma, Why Metastasizes if Benign

SESSION TITLE: Lung Pathology Student/Resident Case Report Posters SESSION TYPE: Student/Resident Case Report Poster PRESENTED ON: Tuesday, October 27, 2015 at 01:30 PM - 02:30 PM INTRODUCTION: Pulmonary benign metastasizing leiomyoma (BML) is a rare condition characterized by pulmonary lesions seen in women with uterine leiomyoma. CASE PRESENTATION: A 23 year old woman with history of irregular vaginal bleeding and fibroids presented with shortness of breath. Physical exam was normal except for swelling of left leg. CT angiogram revealed segmental pulmonary embolism and multiple bilateral pulmonary nodules. She underwent CT guided biopsy of lung lesion and ultrasound guided biopsy of the uterine lesion. Pathological examination revealed both lesions to be a smooth muscle neoplasm and immunohistochemical staining was positive for smooth muscle actin(SMA), desmin and estrogen receptor. Tumor cells did not express S-100, CD34 and C-kit. Staining for Ki-67 revealed expression in 10-15% of the spindle cells. The overall morphological and immunohistochemical features supported the diagnosis of pulmonary angio lipoleiomyoma. An IVC filter was placed and she received leuprolide which resulted in regression of lung nodules and a follow up imaging of the lung at 6 months also documented sustained remission. DISCUSSION: Pulmonary BML commonly presents after myomectomy or hysterectomy. Most common site of metastasis are lungs, other sites include para-aortic lymph nodes and liver. Estrogen has a key role in its proliferation which explains its regression with anti estrogen medications i-e Gonadotropin releasing hormone (GNRH) analog (1). The underlying pathogenesis for metastasis of a benign tumor is unknown. Several hypotheses exist: (A) Proliferation of native lung parenchymal smooth muscles however this does not explain extra pulmonary metastasis; (B) Hematogenous spread after myomectomy or hysterectomy which is not the case in the above presentation; (C) Sampling of non malignant component during biopsy leading to sampling error(2) More than 80% of the PBL cases are found to be multiple nodules on chest imaging but rare cases of solitary nodules are also reported. Diagnostic evaluation is done by CT guided biospy, bronchoscopy or video assisted thoracoscopic surgery(3) CONCLUSIONS: In summary, in a patient with history of fibroids with pulmonary manifestations, Pulmonary BML should be included in the differential diagnosis. A thorough histopathologic evaluation should be performed to exclude a possible malignancy. Reference #1: Radzikowska, E., et al., Benign pulmonary metastasizing leiomyoma uteri. Case report and review of literature. Pneumonol Alergol Pol, 2012. 80(6): p. 560-4. Reference #2: Tietze L., Günther K., Hörbe A., et al. Benign metastasizing leiomyoma: a cytogenetically balanced but clonal disease. Human Pathology. 2000;31(1):126-128. doi: 10.1016/s0046-8177(00)80210-5 Reference #3: Lewis, E.I., et al., Novel hormone treatment of benign metastasizing leiomyoma: an analysis of five cases and literature review. Fertil Steril, 2013. 99(7): p. 2017-24. DISCLOSURE: The following authors have nothing to disclose: Yasir usman, Muhammad Ishaq, ahmed Awab, Maria Palacios No Product/Research Disclosure Information