Massive pulmonary embolism in cancer patients can be due to detached thrombi or tumor. Pulmonary tumor embolism is often undiagnosed antemortem. We report a 52-year-old Chinese man admitted for management of hepatocellular carcinoma (HCC). Computerized tomography showed tumor involvement of hepatic vein and inferior vena cava. He died suddenly on the day of admission. At autopsy the main pulmonary arteries of both lungs were blocked by large tumor emboli, the immediate cause of death. Although rapid death in patients with HCC is usually caused by intraperitoneal hemorrhage from spontaneous rupture of tumor, massive pulmonary tumor embolism should also be considered in these patients, especially when antemortem evidence of hepatic vein and/or inferior vena cava invasion is present.