MKI67 and neoplasm: The Ki-67 index is a measurement of cell proliferation that can be used to predict the long-term recurrence of carcinoid tumors. The Ki-67 is categorized into grades G1 (≤2%), G2 (3-20%), or G3 (>20%) according to the European Neuroendocrine Tumor Society guidelines and the 2010 World Health Organization classification [16] A Ki-67 index of 2% or lower means that fewer than two in every 100 cells (2%) are dividing.