Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (P-NETs) are rare tumors that are usually grouped based on malignancy versus benignity, cell of origin, and functional status. On account of malignancy versus benignity, histopathology cannot reliably differentiate between both categories. Distinction is based on demonstrating invasion of nearby organs, nodal or distant metastasis, undoubtedly marking the tumor as “malignant”. Islets of Langerhans, which constitute the endocrine pancreas, contain only four types of cell, namely alpha, beta, delta, and PP cells secreting glucagon, insulin, somatostatin, and pancreatic polypeptide, respectively. Gastrin, which is commonly secreted from P-NETs, and vasoactive intestinal peptide (VIP) are not normally secreted by adult endocrine pancreas. Functional P-NETs include insulinomas, which are the commonest of these, closely followed by gastrinomas, while the remainder represents a subset of P-NETS called rare functional P-NETS and include VIPoma, glucagunoma, somatostatinoma, and rare others. Several other peptides may be overproduced by PNETs, yet not producing clinical syndromes, hence should be described as nonfunctional P-NETs (NF-PNETs).