MKI67 and neuroendocrine neoplasm: 14. According to the North American Neuroendocrine Tumor Society (NANETS) and European Neuroendocrine Tumor Society (ENETS) guidelines histopathologic biopsy should provide information regarding the histologic classification, the degree of differentiation, and the proliferation-based grading with indication of the Ki-67 index 15,16. Moreover, in accordance with the NANETS and ENETS Guidelines, circulating biomarkers, specifically chromogranin A (CgA) and neuron-specific enolase (NSE), should be collected at baseline for all NET 16,17.