As no mutations were found in classical mutated genes of the Wnt pathway, i.e. APC, ß-catenin, or GSK3ß, we decided to sequence the complete exome of eight canine mammary tumor cell lines; three cell lines with activated basal Wnt signaling and a rounded morphology and five cell lines with a low Wnt activity and a spindle cell morphology. Here, APC is linked to breast cancer.