The prognostic role of Ki67 proliferative index in neuroendocrine tumors (NETs) was identified for the first time in 1996 by two independent Italian research teams [3, 4], and since then, many studies have been performed to evaluate its prognostic, diagnostic, and predictive role in other digestive neuroendocrine neoplasms (NENs). The gene discussed is MKI67; the disease is neuroendocrine neoplasm.