A recent landmark study showed that G3 NECs with a Ki67 index of <55% do not respond to cisplatinum-based chemotherapy, unlike G3 NECs with a Ki67 index >55%.44, 45 This supports the concept that the current WHO G3 category is heterogeneous and that tumors at the lower end of the G3 range are, in fact, WD-NETs with an elevated proliferation rate (or ‘high-grade, WD neuroendocrine tumors’). The gene discussed is MKI67; the disease is Wilson disease.