PIK3CA and breast cancer: With regard to the genomic sequencing (GS) data, it has been reported that RB1, ZFHX3, HER2, ATR, FAT1, ARID1A, ATM, CHEK2, TP53, BRCA1, CDH1, PTEN, COL6A3, FLT3, MLH1, BRCA2, MAP3K1, IGFN1, KMT2D, MET, PIK3CA and KMT2C are the most frequently mutated genes in BC metastases of the central nervous system [14].