We describe a case of minute pancreatic ductal adenocarcinoma featuring stenosis of the main pancreatic duct (MPD) and associated with histological findings of periductal elastosis and fibroblast proliferation. A 53-year-old Japanese man with preoperative radiological evidence of MPD stricture and dilation of the distal MPD, and suspected of having pancreatic cancer, underwent successful resection. Neither radiological nor macroscopic examination directly disclosed any tumorous lesions, and a small focus of carcinoma (8 × 8 mm) was only revealed on microscopic examination. The tumor was a poorly differentiated, invasive ductal adenocarcinoma that had invaded the intrapancreatic nerves and veins. Interestingly, the MPD located at the edges of the tumor had not been destroyed by the carcinoma, but its wall had been thickened by elastic tissue and fibroblast proliferation, resulting in stenosis. The peripheral pancreas exhibited secondary obstructive pancreatitis. To date, the detection of small pancreatic tumor masses using imaging procedures remains difficult, and most patients are diagnosed on the basis of pancreatic ductal changes. However, the published work on small pancreatic cancers contains little information about the histological features of the affected MPD. The present findings suggest that MPD strictures are not always provoked by destruction or filling with cancer cells, and that they can be caused by periductal elastosis and fibroblast proliferation in a minute carcinoma. Such changes in the MPD may therefore be of clinical importance in the detection of early stage cancers.
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