ESR1 and neoplasm: Of interest, the highest frequencies (> 30%) of PIK3CA gene mutations were detected in tumours with more favourable characteristics (G1, G2, ER-positive, PgR-positive, luminal-like, HER2-negative), which is in line with most other studies and available data in the COSMIC database http://www.sanger.ac.uk/cosmic/http://www.sanger.ac.uk/cosmic/ [21].