Rare Functioning Pancreatic Endocrine Tumors

Pancreatic endocrine tumors (PETs) represent a heterogeneous group of tumors depending on functional status and histological differentiation. Functioning tumors are defined when clinical symptoms are related to peptide/hormone overproduction. Tumors secreting pancreatic polypeptide, human chronic gonadotrophin subunits, calcitonin, neurotensin or other peptides do not usually produce specific symptoms and should be considered as non-functioning tumors. In addition, it is important to note that several of these rare functioning tumors (RFTs) may have extra-pancreatic localizations such as VIPomas (10%), somatostatinoma ( similar to 50%), GRFoma (70%) and adrenocorticotropic-secreting tumors (ACTHoma) (85%) [1].