A Vascular Mimicker: Inferior Vena Cava Leiomyosarcoma Presenting with Pseudo Right Heart Failure and a Massive “Snake Thrombus”

Introduction: Inferior vena cava syndrome (IVCS) often presents with symptoms such as dyspnea and peripheral edema, leading to clinical confusion with right heart failure (RHF). While primary IVC leiomyosarcoma is an exceedingly rare malignancy, its insidious growth can cause significant vascular obstruction and mimic cardiac pathologies, particularly when associated with elevated cardiac biomarkers.Case Report: A 52-year-old male presented with progressive dyspnea and generalized edema. Initial suspicion of RHF was supported by an elevated Pro-BNP level of 395 ng/L. However, echocardiography showed a normal ejection fraction. Abdominal CT subsequently revealed a 9 cm aortocaval mass and an obstructive "snake thrombus" extending from the right femoral vein into the right atrium, classified as a Mayo Level IV thrombus. Histopathological examination confirmed IVC leiomyosarcoma. Despite starting radiotherapy, the patient's status rapidly deteriorated, and he passed away within the same month.Conclusion: IVC pathologies must be considered as a primary differential in patients presenting with RHF symptoms and elevated Pro-BNP levels but preserved cardiac function. Early identification of rare, invasive vascular tumors and mobile "snake thrombus" is vital for preventing lethal complications like pulmonary embolism.