Endocrine Abstracts

In the gastroentero-pancreatic tract, a spectrum of neuroendocrine tumors (NET) exists, including low grade tumors (carcinoid), intermediate grade malignant carcinoid, and high grade poorly differentiated carcinomas of the small and large cell types. In year 2000, the WHO presented a classification scheme for all NETs, but mostly applied to gastroentero-pancreatic tumors. This term carcinoid was replaced by (neuro)endocrine tumor, malignant carcinoid by well differentiated (neuro)endocrine carcinoma, and the term “small cell carcinoma” was confirmed for poorly differentiated NE neoplasms. The new terminology induced some confusion in the routine application and interpretation of some NETs, especially those of intermediate grade (which underwent major changes in the new classification). New diagnostic criteria pose problems to the pathologist (e.g. correct diagnosis on scarce biopsy or cytological material) and to the clinician (choice of the appropriate therapy for single histological types). The characterization of NETs includes the immunoprofiling of NE differentiation markers and hormonal products, but also the analysis of prognostic (i.e. Ki67) and therapeutic factors. The latter include somatostatin receptor expression profile (possible in surgical, biopsy or cytology specimens by immunohistochemistry), to identify possible targets of somatostatin analogs. Finally, apart from pure endocrine tumors, NE differentiation occurs also in non-endocrine tumors (see review in Volante M, Virchows Arch 449:499, 2006). “Mixed endocrine-exocrine carcinomas”, as well as gastric, colorectal and pancreatic adenocarcinomas with foci of NE differentiation have been described. These latter tumors can account for up to 20% of cases, depending on the method used to assess the NE phenotype (eg chromogranin A immunostaining), but to date they were not found to bear any prognostic significance (as opposed to the well established prognostic role of NE differentiated prostate cancer), with the possible exception of gastric cancer, according to a recent study by Japanese authors (Jiang SX, Am J Surg Pathol 30:945, 2006).