This number is comparable to the number of changes observed in myelocytomatosis oncogene (c-myc)-induced mouse mammary tumors (Weaver et al. 1999) and human tumors (Ried et al. 1995), yet less than the number of changes seen in breast cancer 1 (Brca1)-deficient mouse tumors (8.0) and more than v-erb-b2 erythroblastic leukemia viral oncogene homolog 2 (HER2/neu)-induced tumors (2.8) (Montagna et al. 2002; Weaver et al. 2002). This evidence concerns the gene ERBB2 and breast cancer.