PIK3CA and breast cancer: After the chi-square test, 15 mutated genes, including PIK3CA, TP53, MUC16, GATA3, SYNE1, MAP3K1, DNAH11, CDH1, AKAP9, CBFB, RB1, CTCF, SMAD4, GPS2, and JAK1, showed significant differences (FDR < 0.01) among the breast cancer subtypes (Figure 5A).