A case of acinar cell carcinoma of the pancreas that formed extensive tumor thrombus of the portal vein.

A 58-year-old man was admitted to our hospital because of anorexia and back pain. He had been previously diagnosed with chronic pancreatitis with blood thrombus of the splenic vein at another hospital. Abdominal ultrasonography and computed tomography revealed a large mass in the body and tail of the pancreas, which directly invaded the stomach and the spleen. Small nodular metastases in both lungs were also detected. Furthermore, tumor thrombus continuously involved the splenic and proximal superior mesenteric vein, main portal vein, and its right intrahepatic branch. A metastatic mass was disclosed in the adjacent liver. The specimens obtained from portal tumor thrombus were histologically compatible with acinar cell carcinoma. Portal tumor thrombus is a rare condition in pancreatic tumors; however, it seems to be important to differentiate tumor thrombus from blood thrombus of the portal vein in order to know the true clinical stage and provide a suitable treatment.