The WHO 2010 classification of neuroendocrine neoplasms (NEN) (1) distinguishes well to moderately differentiated neuroendocrine tumors (NET), which are graded depending on their proliferation status into NET G1 (Ki-67 index < 2%), and G2 (Ki-67 2–20%), from poorly differentiated, highly malignant neuroendocrine carcinomas (NEC G3, Ki-67 >20%). Here, MKI67 is linked to neuroendocrine neoplasm.