Introduction to a revised clinicopathological classification of neuroendocrine tumors of the gastroenteropancreatic tract.

A revised clinicopathological classification of neuroendocrine tumors of the gastroenteropancreatic tract has been recently developed under the auspices of the World Health Organization (WHO) according to advances in the field of tumor biology. Here the classification is briefly outlined and discussed together with the guidelines for a correct approach to the histopathological diagnosis of neuroendocrine tumors and the interpretation of the classification schemes covering clinical (hyperfunctional syndromes included), pathological and biological patterns, with special emphasis on tumor prognosis.