PIK3CA and breast cancer: Examination of the existing literature reveals that, in addition to DMBA-induced mammary tumors, other mouse models that show a similarly high presentation of squamous-like mammary tumors are the Brg1+/− [17] and Pik3ca-H1047R [18] models, the squamous tumors of which were shown by gene set analysis to be similar to claudin-low human breast tumors [19].