Abstract 4139444: Benign Metastasizing Leiomyoma: A Challenging Case with Multifocal Involvement in the Heart, Liver, and Uterus

Case Presentation: A 39-year-old Southeast Asian female presented with fatigue and exertional dyspnea. She underwent a myomectomy four years ago. Examination showed vital signs within normal limits, except for an SpO2 of 87%. Blood tests indicated microcytic hypochromic anemia and elevated D-Dimer levels of 1479 ng/mL. A transthoracic echocardiogram revealed a large mass occupying almost the entire right atrium, extending into the inferior vena cava. A CT scan showed a large, low attenuation, and minimally enhanced mass extending from the right atrium into the inferior vena cava and right hepatic vein, possibly invading segments VII-VIII of the liver (Figure 1). Abdominal CT and MR images revealed multiple degenerating uterine fibroids, bilateral dilated uterine tubes, and mild right hydronephrosis (Figure 2). The patient underwent surgical removal of the cardiac mass under general anesthesia with extracorporeal circulation and hypothermia. Pathological examination confirmed a benign tumor characterized by bundles of smooth muscle cells (Figure 3). Immunohistochemical staining with Actin (+), Progesterone receptor (+), Desmin (+), Ki67 (+) was consistent with a diagnosis of benign metastasizing leiomyoma (BML) of the heart. Subsequently, elective hysterectomy and bilateral salpingo-oophorectomy were performed. Discussion: Although rare, uterine leiomyoma can exhibit metastatic behavior, disseminating to extraneous anatomical sites. BML should be considered in the differential diagnosis when patients present with an atypical cardiac mass and have a history of uterine leiomyoma, myomectomy, or hysterectomy. BML of the heart is an exceptionally rare condition, predominantly affecting middle-aged women who have undergone hysterectomy or myomectomy. While BML commonly occurs in pre-menopausal patients and shares a potentially similar mechanism with endometriosis, as indicated by its response to estrogen-blocking agents, the occurrence of BML in post-menopausal women suggests the involvement of other contributing factors. Multiple imaging modalities play a significant role in the diagnosis and preparation for surgical management.