The recent 2017 WHO classification (Table 1), based on the degree of differentiation and Ki-67 index, divides PanNENs into well-differentiated tumors (PanNETs), further divided into PanNETs-G1 (Ki67 index ≤ 3%), PanNETs-G2 (Ki67 index between 3% and 20%), and PanNETs-G3 (Ki67 index ≥ 20%), and carcinomas (PanNECs) which exhibit poorly differentiated morphology [14,15,16]. This evidence concerns the gene MKI67 and carcinoma.