MKI67 and neuroendocrine neoplasm: Based on WHO digestive system classification,[19] neuroendocrine tumors were classified into three categories, which are G1: mitotic < 2/10 HPF and/or PI < 2%; G2: mitotic < 2–20) / 10 HPF and/or PI < 3% to 20%; Neuroendocrine carcinoma (NEC): mitosis > 20/10 HPF and/or Ki-67 PI > 20%.