NETs can be classified according to the new WHO classification in four categories based on tumor grade, cancer cell morphology, proliferation index (Ki-67 index), and mitotic count as well as the presence of necrosis: well-differentiated NETs G1, G2, and G3 and poorly differentiated neuroendocrine carcinomas (NECs), representing 10–20% of all neuroendocrine neoplasms [5]. The gene discussed is MKI67; the disease is neoplasm.