PIK3CA and invasive breast carcinoma: Our results indicate that: (a) PIK3CA hotspot mutations are present at high frequencies in DNAs isolated from CellSearch® cartridges and paired plasma‐ctDNA both in early and metastatic BrCa, (b) the concordance between plasma‐ctDNA and CTCs is higher in the metastatic setting, (c) PIK3CA mutational status significantly changes after therapeutic intervention, and (d) PIK3CA mutation detection in CTCs and plasma‐ctDNA provides complementary information.