Considering the proposal of a common classification framework to unify the nomenclature of neuroendocrine neoplasms (NENs) arising in different organs, which is based on morphological differentiation and proliferation [7], the role of Ki67 proliferative index may be important to better define PitNETs and to stratify them in different prognostic categories. This evidence concerns the gene MKI67 and neuroendocrine neoplasm.