Based on differentiation and grading, pNENs can be categorized into four main groups: NET G1 (well-differentiated, Ki67 < 3%), NET G2 (well-differentiated, Ki67 3–20%), NET G3 (well-differentiated, Ki67 > 20%), and NEC (poorly differentiated) [2]. The gene discussed is MKI67; the disease is neuroendocrine carcinoma.