Which tumor is the most common primary caval neoplasm of the inferior vena cava?

• A. Renal cell carcinoma
• B. Leiomyosarcoma
• C. Hepatocellular carcinoma
• D. Lymphoma

Answer: (B)

Tumors that originate inside the wall of the inferior vena cava are extremely rare, but when they do occur, the most common one is leiomyosarcoma. This cancer arises from the smooth muscle cells of the venous wall, so it is considered a primary caval neoplasm rather than a tumor that started in another organ and then spread into the IVC. Leiomyosarcoma tends to grow along or within the vessel, and it can extend into the heart in advanced cases, which is a recognizable pattern on imaging.

Other tumors listed—renal cell carcinoma, hepatocellular carcinoma, and lymphoma—usually arise in the kidney, liver, or lymphoid tissue, respectively, and may invade or compress the IVC secondarily. They are not primary cancers of the IVC itself, which is why leiomyosarcoma is the best answer for the most common primary caval neoplasm.