MKI67 and neuroendocrine neoplasm: Gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) with a Ki67 proliferation index above 20% are a heterogeneous group of rare, highly malignant neoplasms associated with a poor prognosis [1] Immunohistochemically assessed tumour expression of synaptophysin and/or CgA is mandatory for the NEN diagnosis.