MKI67 and neuroendocrine carcinoma: Tumors are divided into NET grade 1 (mitotic activity <2/10 high-power fields and ≤2% Ki-67 index), NET grade 2 (mitotic activity 2–20/10 high-power fields and/or 3–20% Ki-67 index level), and neuroendocrine carcinoma (mitotic activity >20/10 high-power fields and >20% Ki-67 index level).