A detailed analysis of the COSMIC (Catalogue Of Somatic Mutations in Cancer, UK) database revealed that PIK3CA is indeed most frequently mutated in breast cancer (28.83%), especially in estrogen receptor (ER)-positive carcinomas (38.88%), as well as endometrium (27.39%) and urinary tract (20.2%) cancers (Table 1). The gene discussed is ESR1; the disease is cancer.