A 58-year-old man who complained of an abdominal tumor was admitted to our hospital. Abdominal CT scan showed that a 15-cm tumor occupied the entire right upper abdomen and that there were ascites and liver metastases. A liver biopsy was performed. The liver biopsy showed a small cell carcinoma pattern, but no definitive origin of the tumor was determined. Considering the extensive peritoneal invasion and multiple liver metastases, he received 2 / courses of cisplatin/etoposide chemotherapy, but his tumor became larger with concomitant abdominal pain and nausea. The patient suddenly died due to multiple organ failure caused by tumor necrosis. The autopsy revealed a pathological diagnosis of primary small cell carcinoma of the pancreas.