Cases with discordance between PIK3CA mutation level and treatment response could be explained by the technology used (Kodahl et al., 2015) or the disease stage (early‐stage versus advanced breast cancer; Garcia‐Saenz et al., 2017; Kodahl et al., 2015), or may reflect tumor evolution and heterogeneity within advanced breast cancer disease. This evidence concerns the gene PIK3CA and breast cancer.