MKI67 and pancreatic neuroendocrine tumor: Currently, there are three grades of pNENs: pancreatic neuroendocrine tumors (pNETs) of Grade 1 (G1, well differentiated (WD), ki67 < 2%), Grade 2 (G2, WD, ki67 between 2–20%), and Grade 3 (G3, WD, Ki67 > 20%) [4].