Conundrums and Caveats in Neuroendocrine Tumors of the Pancreas.

Pancreatic neuroendocrine tumors (Pan-NETs) are the second most common epithelial neoplasm of the pancreas after ductal adenocarcinoma. They can be clinically defined as functional, nonfunctional, and hereditary. This review addresses typical and atypical pathologic features of Pan-NETs, with a focus on practical issues involved in differential diagnosis, immunohistochemical work-up, intraoperative frozen section interpretation, sources of diagnostic errors, and classification. The diagnosis of a Pan-NET requires analysis of all available clinical and radiographic information and pathologic characteristics of the tumor, and it is crucial to understand the clinical impact of the pathologic interpretation.