MKI67 and neuroendocrine carcinoma: Gastroenteropancreatic (GEP)-NENs are divided into grade (G) 1 and G2, G3 neuroendocrine tumors (NETs) that have well-differentiated morphology and Ki-67 ≤2% for G1, 3-20% for G2 and >20% for G3, and neuroendocrine carcinomas (NECs) with poorly differentiated morphology and Ki-67 >20% (2, 3).