PNETs were originally classified into three distinct categories: (1) G1, which are well-differentiated PNETs and characterized by mitoses <2/10 high-power field (HPF) and Ki67 index <3%; (2) G2, which are well-differentiated PNETs with mitoses ranging from 2 to 20/10 HPF or Ki67 index between 3% and 20%; (3) G3, which are poorly differentiated and also called pancreatic neuroendocrine carcinomas (PNECs) with mitoses exceeding 20/10 HPF or Ki67 index surpassing 20%. The gene discussed is MKI67; the disease is pancreatic endocrine carcinoma.