MKI67 and neoplasm: According to the European Neuroendocrine Tumor Society (ENETS) and the current WHO 2019 classification for GEP-NENs, GEP-NENs are classified in relation toKi-67 into well-differentiated NENs (G1-high mature: Ki-67 < 3%, G2-medium mature: Ki-67 3–20%, G3-low mature: Ki-67 > 20%), poorly differentiated NECs (always G3) and mixed neuroendocrine–non-neuroendocrine neoplasms (MiNENs) [4,5].