Small pancreatic cancer with pancreas divisum preoperatively diagnosed by pancreatic juice cytology.

We present a case of small pancreatic head cancer with pancreas divisum preoperatively diagnosed by pancreatic juice cytology. A 60-year-old woman was referred to our hospital for evaluation of a dilated main pancreatic duct (MPD). A small and poorly reproducible low-echoic lesion in the pancreas was suspected by ultrasonography (US) and endoscopic ultrasonography (EUS). Magnetic resonance cholangiopancreatography (MRCP) failed to visualize the ventral pancreatic duct, and the upstream dorsal pancreatic duct was dilated. Endoscopic retrograde cholangiopancreatography (ERCP) was indicative of pancreas divisum, and complete obstruction of the MPD in the pancreatic head was seen. Cytology of pancreatic juice obtained from the dorsal pancreas after minor papilla sphincterotomy revealed the presence of adenocarcinoma cells. Pancreatoduodenectomy was performed under the diagnosis of pancreatic head cancer with pancreas divisum. Histological examination revealed moderately-differentiated tubular adenocarcinoma 20 mm in diameter, located in the pancreatic head. Dilatation of the dorsal pancreatic duct is sometimes observed in cases with pancreas divisum without the presence of tumors. When pancreatic duct stenosis also exists in such cases, even if a tumor is not clearly visualized by diagnostic imaging, vigorous examinations such as pancreatic juice cytology are recommended to establish an accurate diagnosis.