A malignant nonfunctioning pancreatic endocrine tumor with a unique pattern of intraductal growth.

The intraductal growth of nonfunctioning pancreatic endocrine tumors (NFPTs) is considered to be rare, and in our survey of the English-language literature, we found only three cases to have been described previously. We herein report the case of a 36-year-old man with a malignant NFPT that uniquely grew within the lumen of the main pancreatic duct (MPD) and completely obstructed the MPD, as shown by endoscopic retrograde pancreatography (ERP). Endoscopic ultrasonography clearly detected the tumor with intraductal growth.