PIK3CA and neoplasm: Furthermore, in a series of early-stage BC cases, several genes were found to be frequently mutated in tumour cells, including TP53 (41% of tumours), PIK3CA (30%), MYC (20%), PTEN (16%), CCND1 (16%), ERBB2 (13%), FGFR1 (11%), and GATA3 (10%) [2,11].