A 62-year old woman presented a fistula due to a previously made cystojejunostomy performed because of a small pancreatic lesion considered as a pseudocyst. This intervention was performed in another institute. In the course of the exploration the authors resected the whole mass with the Roux-en-Y loop, and with the spleen. The histological examination proved a cystadenocarcinoma of the pancreas. There are discussed the problems of the intraoperative diagnosis of pancreatic lesions, and the possibilities of the reduction of mistakes. The authors emphasize the experience of the surgeon--which is the most important factor of the cure--and the importance of the fine needle biopsy.