MKI67 and neuroendocrine neoplasm: Well-differentiated GEP-NENs are considered to be neuroendocrine tumors and are graded as G1 (mitotic count <2 per 10 high power fields (HPFs) and/or Ki67 ≤ 2%) or G2 (mitotic count 2–20 per 10 HPFs and/or Ki67 3–20%).