MKI67 and neuroendocrine carcinoma: In addition, NET are graded based on the mitotic rate and Ki67 index as NET grade (G) 1 (Ki-67 < 3%), NET G2 (Ki-67 = 3–20%), and NETG3 (Ki-67 > 20%), whereas NEC are subdivided into large- and small-cell NEC based on morphological features [5].