APC and breast cancer: The majority of mammary tumors developed in K14-cre; ApcCKO/+ mice had ApcΔ580/+ genotype and have somatically acquired truncation mutation in the remaining wild-type allele, unlike intestinal tumors in ApcΔ580/+ mice and other germline Apc heterozygotes in which the preferential mechanism of the wild-type Apc is allelic loss [14], [30]–[32].