Multiple mouse models of the PI3K pathway-driven cancer have recently been developed to investigate the impact of PI3K mutation or combination of other related mutations on breast cancer development under the control of MMTV LTR or WAP promoter.17, 18, 19, 20, 21 However, the role of PI3K activation in tumor initiation, progression and phenotype is not well understood. The gene discussed is PIK3CA; the disease is breast carcinoma.