In the present study, we introduced mutant PIK3CA oncogene, which is known to be widely mutated in breast tumors, together with mutant Ras (widely used gene to in vitro transform mammary epithelial cells) and mutant p53 in two different stem/progenitor cell types K5+/K19- or K5+/K19+ and then assessed the effect of the oncogene combination in driving pathogenesis from the two isogenic cell lines. The gene discussed is PIK3CA; the disease is breast neoplasm.