In our sequence-based studies of 17 K14-cre; ApcCKO/+, five WAP-cre; ApcCKO (ApcCKO/CKO and ApcCKO/+ combined), and three ApcΔ580/+ mammary tumors, activating mutations were found at codons 12 and 61 of either H-Ras or K-Ras only in a subset (7 of 17) of K14-cre; ApcCKO/+ tumors but none from other models. Here, KRAS is linked to breast cancer.