The 2010 World Health Organization (WHO) classification of gastroenteropancreatic (GEP)-NENs divided NENs on the basis of the mitotic count and/or the Ki67 labeling index (LI) in low-intermediate grade (G1-G2) and well differentiated (WD) morphology forms, named “neuroendocrine tumors” (NETs), and high grade (G3) and poorly differentiated (PD) morphology ones, named “neuroendocrine carcinomas” (NECs). The gene discussed is MKI67; the disease is neuroendocrine carcinoma.