MKI67 and neuroendocrine carcinoma: The 2010 WHO classification, instead, considers the proliferative activity of the tumours on the basis of their expression of the Ki-67 index or the mitotic count [1-10], and it divides the tumours into neuroendocrine tumour (NET) of low grade, neuroendocrine tumour of intermediate grade and neuroendocrine carcinoma (NEC - high grade).