Molecular characteristics of colorectal neuroendocrine carcinoma; similarities with adenocarcinoma rather than neuroendocrine tumor

Summary To further clarify the molecular features of colorectal neuroendocrine carcinomas (NECs), we immunohistochemically examined tumor samples from 25 NECs, including 9 small cell NECs (SCNECs) and 16 large cell NECs (LCNECs), 20 neuroendocrine tumors (NETs), and 21 poorly differentiated adenocarcinomas (PDCs) for the expression of several biomarkers (p53, β -catenin, Bcl-2, Rb, p16, p21, cyclin D1, and cyclin E) and used sequencing analysis to identify gene alterations of TP53 , APC , CTNNB1 , KRAS , and BRAF . The frequencies of aberrant p53 expression (88%), β -catenin nuclear expression (48%), and high expression of cyclin E (84%) were significantly higher in NECs than in NETs (0%, 5%, and 5%, P TP53 , APC , KRAS , and BRAF gene mutations were variously detected in NECs and PDCs but not in any NETs. The frequencies of decreased expression of Rb (56%) and high expression of p16 (56%) and Bcl-2 (64%) were significantly higher in NECs than in PDCs (5%, 19%, and 5%, P P P