MKI67 and neuroendocrine carcinoma: The World Health Organization (WHO) introduced the following sub-group to a new grading system for pNETs in 2017: well-differentiated neuroendocrine tumors (NETs) with a Ki-67 >20%, defined as grade 3 pNET, which is clearly different from poorly differentiated neuroendocrine carcinoma, defined as grade 3 pNEC (5, 6).