To explore PTPN13 role in breast tumor development in a relevant genetically-modified mouse model, we crossed mice that lack PTPN13 catalytic domain (PTP-BL-ΔP) or not (PTP-BL-wt) 9 with MMTV-HER2 transgenic mice in which 70% of females develop mammary carcinoma before one year of age 32. Here, ERBB2 is linked to breast carcinoma.