Intravascular extension of uterine sarcoma: A rare presentation mimicking venous thromboembolism.

Uterine leiomyosarcoma (ULMS) is a highly aggressive mesenchymal malignancy. While hematogenous spread is common, malignant intravenous leiomyosarcomatosis (IVLS) with extension into the heart is an exceptional and life-threatening phenomenon that presents significant diagnostic and therapeutic challenges. A 57-year-old postmenopausal woman presented with a voluminous pelvic mass. Initial MRI identified a high-grade ULMS with extensive local invasion and tumor thrombosis of the left ovarian vein. Following neoadjuvant chemoradiotherapy and total hysterectomy, the patient developed acute respiratory distress. Emergency echocardiography and CT angiography revealed a massive tumor thrombus extending from the iliac veins and inferior vena cava (IVC) into the right atrium, complicated by bilateral lobar pulmonary embolism. Despite an emergency beating-heart thrombectomy and intensive care support, the patient succumbed to refractory cardiogenic shock. This case underscores the critical role of multi-parametric MRI and CT angiography in identifying malignant intravascular extension. Differentiating tumor thrombi from bland venous thromboembolism is essential, as IVLS requires aggressive, multidisciplinary surgical management. Systematic vascular screening should be mandatory in cases of aggressive uterine malignancies to prevent fatal embolic events.