Is the pathologist indispensable in gastrointestinal stromal tumors and neuroendocrine tumors?

Neuroendocrine tumors (NETs) and gastrointestinal stromal tumors (GISTs) are different tumor categories with no pathogenetic, morphologic, clinical, or therapeutic similarities: NETs are epithelial to neural tumors in contrast to GISTs, which show mesenchymal cell lineage. Both tumors, however, arise more frequently from the gastrointestinal tract and may benefit of specific target therapeutic approaches: imatinib/STI-571 for GISTs and m-Tor pathway inhibitors or somatostatin analogs for NETs. The role of pathologist is crucial when dealing with both NETs and GISTs, as morphological, immunohistochemical, and molecular analysis often provide helpful information on the clinical behavior and management. We here propose a general overview on nomenclature of tumors classification and suggestions for histological report of both NETs and GISTs. Moreover, we will approach in finer details the immunohistochemical analysis on origin and differential diagnosis in NETs as well as the prognosis and resistance to therapy in GISTs. This review emphasized recent literature advances regarding similarities and differences in the managerial pathologist's approach to either tumor type.