For gastro-entero-pancreatic (GEP)-NENs, the World Health Organisation (WHO) tumour grade is defined by the percentage of tumour cells with a nuclear expression of Ki-67 and morphological differentiation features (well-differentiated (called neuroendocrine tumour (NET)) vs. poorly-differentiated (called neuroendocrine carcinoma (NEC))) [5,6,7]. This evidence concerns the gene MKI67 and neoplasm.