PIK3CA and breast cancer: These genes included TP53, PIK3CA, FAT3, APOB, GATA3, USH2A, FRAS1, HUWE1, and PCDH15. Notably, TP53 had the highest mutation rate in BC-ImH and the lowest mutation rate in BC-ImL (BC-ImH (45.7%) versus BC-ImM (25.7%) versus BC-ImL (24.2%)).