MKI67 and neuroendocrine neoplasm: In the WHO classification from 2010, all neuroendocrine neoplasms (NEN) with a proliferation rate (Ki67) > 20% had been classified as poorly differentiated grade 3 neuroendocrine carcinomas (NEC) in contrast to well differentiated grade 1 and 2 neuroendocrine tumors (NET G1/G2) [1].