Primary leiomyosarcoma of the inferior vena cava (IVC-LMS) is an exceptionally rare vascular malignancy that often poses diagnostic and surgical challenges. We report the case of a 65-year-old woman who presented with a large infra-renal IVC mass. Contrast-enhanced MRI demonstrated a lobulated lesion with heterogeneous enhancement, central necrosis, and restricted diffusion in the solid components. The presence of an “IVC claw sign” confirmed its vascular origin. The mass closely abutted the liver, pancreas, and right kidney without evidence of invasion, and both renal veins were preserved. The patient underwent complete en bloc tumor excision with IVC reconstruction using a collagen-coated polyester (INTERGARD) graft following Cattell–Braasch exposure. Postoperative CT imaging confirmed total tumor removal and graft patency. This case underscores the crucial role of MRI in defining the vascular origin and extent of the tumor, facilitating precise surgical planning, and demonstrates the feasibility of successful IVC reconstruction using synthetic vascular grafts.

Inferior vena cava (IVC) leiomyosarcoma; Contrast-enhanced MRI; IVC reconstruction; Vascular graft (INTERGARD); Retroperitoneal tumor; Rare vascular malignancy