Neuroendocrine tumors are classed as NET G1 (carcinoid, mitotic count of <2 per 10 high power fields (HPF) and/or a Ki67 index of ≤2%); NET G2 (mitotic count of 2–20 per 10 HPF and/or a Ki67 index of 3–20%); and NET G3 (neuroendocrine carcinoma, mitotic count of >20 per 10 HPF and/or a Ki67 index of >20%). Here, MKI67 is linked to neuroendocrine carcinoma.