CTNNB1 and breast carcinoma: Although Wnt signaling was first described as inducing breast tumors in mice [98] and Wnt/β-catenin signaling is activated in a proportion of multiple subtypes of human breast cancers [10,99], the typical mutations in components of the pathway found in CRC (APC, CTNNB1, AXIN2) are rare in breast carcinomas [27].