Abstract
BACKGROUND: Intravenous and intracardiac leiomyomatosis (IVL/ICL) are rare benign smooth-muscle tumors that can extend from pelvic veins into the right heart, often mimicking thrombus or malignancy. CASE SUMMARY: A 51-year-old woman with uterine fibroids was referred for evaluation of a right atrial mass initially suspected to be thrombus. Multimodality imaging, including echocardiography, computed tomography, magnetic resonance imaging, positron emission tomography, venography, and intravascular ultrasound, identified a highly vascular intraluminal mass extending from the right gonadal vein through the inferior vena cava into the right atrium, consistent with IVL/ICL. She underwent single-stage en bloc resection, and pathology confirmed a benign leiomyoma. DISCUSSION: This case highlights the pivotal role of multimodality imaging in early diagnosis and multidisciplinary surgical planning, preventing treatment delay and improving outcomes. TAKE-HOME MESSAGE: Multimodality imaging is essential for early and accurate diagnosis of IVL/ICL and for guiding safe, complete resection.