Neuroendocrine carcinoma (NEC) of the pancreas is very rare, and its origin is not fully elucidated. Here, we present a case of a small-size NEC of the pancreas that is genetically similar to invasive ductal adenocarcinoma (IDA). A 65-year-old man was referred to our hospital due to obstructive jaundice and found to have a 12-mm solid tumor in the pancreas head. The tumor exhibited low vascularity on enhanced computed tomography, and endoscopic retrograde pancreatographic imaging revealed an irregular obstruction in a branch duct of the pancreas. The patient was thereby diagnosed with a pancreatic ductal cancer, and stomach-preserving pancreaticoduodenectomy with regional lymph node resection was performed. Histochemical analysis of the resected tumor showed that the neoplastic cells with scanty cytoplasm and hyperchromatic nuclei strongly expressed chromogranin A and synaptophysin. The Ki-67 index was 40 % in the most proliferative tumor regions, and the tumor was diagnosed as a NEC of the pancreas. However, in the analysis of genetic alterations of the tumor tissue, the neoplastic cells showed altered KRAS, TP53, and SMAD4/DPC4, suggesting that the NEC in our case is genetically related to IDA. Our data suggest that poorly differentiated IDAs may transform into NECs.
Keywords: KRAS; Neuroendocrine carcinoma; Pancreatic cancer; SMAD4; p53.