The most recent classifications of the 7th American Joint Committee on Cancer/Union International Contre le Cancer 2009 (AJCC/UICC) and of the European Neuroendocrine Tumor Society 2006 (ENETS), associated with the WHO classification 2010, segregate NETs into well-differentiated neuroendocrine tumors (low and intermediate grade based on the Ki67 labeling index, also named NET-G1 or carcinoid and NET-G2, resp). The gene discussed is MKI67; the disease is neoplasm.