The patient was a 67-year-old man under follow-up after gastric cancer surgery. An abdominal CT scan performed 1 year earlier had shown an approximately 14-mm hypovascular mass in the pancreatic body; however, he did not consent to treatment and was followed up for 1 year. A blood workup showed that the fasting blood glucose level, which had been within normal limits, was elevated to 174 mg/dl (normal, 70–109 mg/dl), and the HbA1c level was 12.0% (normal, 4.3–5.8%). Abdominal CT revealed an approximately 20-mm mass in the pancreatic body and an approximately 12-mm mass in the pancreatic tail, and magnetic resonance imaging cholangiopancreatography (MRCP) showed discontinuity of the main pancreatic duct (MPD). Since these findings led to the suspicion of invasive ductal carcinoma (IDC) of the pancreas developing in the pancreatic body and tail, we performed distal pancreatectomy with splenectomy. Histologically, IDCs were observed in the pancreatic body and tail. However, PanIN was not observed in the MPD between the two carcinomas. They were diagnosed as independent invasive ductal carcinomas of the pancreas.