MKI67 and neuroendocrine carcinoma: NEN is histopathologically divided into grade 1 NET (G1, Ki-67 < 3%), grade 2 NET (G2, Ki-67 3–20%), grade 3 NET (G3, Ki-67 > 20%), poorly differentiated NEC (small cell/large cell subtypes, Ki-67 usually > 55%) and mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) [2••].