The new WHO book classifies anal adenocarcinomas as primary if arising from mucosal glandular epithelium, which shares the same immunoprofile as colorectal adenocarcinoma (CK7+/−, CK20+/CDX2+), or from anal glands, which shares the same immunoprofile as skin adnexal carcinoma (CK7+/CK20−/CDX2-) [13]. This evidence concerns the gene CDX2 and colorectal adenocarcinoma.