PIK3CA and cancer: Of the 64 codons affected, 6 (3 in TP53, 2 in PIK3CA and 1 in GNAS) are known driver mutations, 4 introduced stop codons into TP53, and 26 occurred within genes whose involvement in cancer is strongly suspected (Table S9 and http://www.sanger.ac.uk/genetics/CGP/Census).