MKI67 and neoplasm: In accordance with the most recent WHO/ENETS criteria, tumor grading is the most common denominator for survival: grade 1 and 2 neuroendocrine tumors (G1-/G2NET) are regarded as well- to moderately differentiated tumors with a low Ki67 index (<3% and 3–20%, respectively); grade 3 NET (G3NET) as well- or moderately differentiated NET with high Ki67 index >20%; and neuroendocrine carcinomas (NEC) as poorly differentiated and with highly proliferative tumors (Ki67 index is most commonly >55%) [1,2,3].