The previous classification published in 2000 categorized GEP-NENs into three groups (well-differentiated endocrine tumor, well-differentiated endocrine carcinoma, poorly differentiated endocrine carcinoma/small cell carcinoma) [9], whereas the 2010 classification categorizes them into NET G1, NET G2 and NEC on the basis of the Ki-67 proliferation index and mitotic count [5]. Here, MKI67 is linked to small cell carcinoma.