In the COSMIC (Catalogue of Somatic Mutations in Cancer) database, PIK3CA H1047R and E545K represent the two most commonly identified PIK3CA mutations in human tumours, accounting for 55% and 24% respectively of all PIK3CA mutations detected in breast cancer and 38% and 27% respectively of PIK3CA mutations in all cancers. The gene discussed is PIK3CA; the disease is neoplasm.