MKI67 and neuroendocrine carcinoma: Whereas the recent, population-based registry publications [38,39] define high-grade as poorly differentiated without considering the proliferation rate (Ki67), the NORDIC NEC trial [16] and several other retrospective treatment trials [21,31,32,35] used the 2010 WHO classification, defining NEN G3 as Ki67 above 20% but not differentiating between NET G3 and NEC.