To explore the possibility, we developed a stochastic model of human breast cancer by breeding STK11fl/f mice (FVB) [21] with mice genetically engineered to express activated Neu/HER2-MMTV-Cre (FVB) under the endogenous Erbb2 promoter, referred to as NIC mice [20], to generate STK11−/−/NIC mice. This evidence concerns the gene ERBB2 and breast cancer.