The main differences in comparison with the 2010 classification are the Ki-67 index of NEN G1 tumours that was altered to less than 3% (instead of ≤2%) and an additional NEN G3 subcategory that was added to the well-differentiated NENs, with a labelling index of more than 20% for Ki-67 or more than 20 mitotic counts per 10 HPF. The gene discussed is MKI67; the disease is neoplasm.