The genomes of two highly used mouse models of breast cancer were recently analyzed and compared to human genomic data, showing that: (a) MMTV-Neu tumors display CNV involving the genes collagen type 1 alpha 1 (Col1a) and chondroadherin (Chad), an amplification that was particularly observed in HER2+ breast cancers; PyMT tumors displayed a highly conserved mutation in the gene coding the protein tyrosine phosphatase receptor (ptphr), resulting in elevated EGFR activity and consequent sensitivity to the EGFR inhibitor erlotinib [431]. This evidence concerns the gene PTPRT and breast cancer.