Thirty 4-week female BALB/c-nu/nu mice were unilaterally injected into mammary fat pad with HER2-positive breast cancer cells SKBR3 (5×106/125 μl/site) and 24 of the 30 mice formed palpable tumors after 15 days (about 200 mm3). Here, ERBB2 is linked to breast carcinoma.