In MSK-2018, significantly higher levels of PIK3CA CN were observed in metastatic HR + /HER2− compared to primary BC samples, both in tumors unselected for PIK3CA mutations (p = 5.3e−24), and in PIK3CA mutant and wt tumors (Fig. 1g and Supplementary Fig. 2). This evidence concerns the gene PIK3CA and breast cancer.