Recently, PIK3CA variant detection in cfDNA was established as a companion diagnostic in clinical practice for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) patients by FDA approval of the selective PI3Kα inhibitor Alpelisib for patients presenting PIK3CA variants in tumor tissue or plasma. Here, ERBB2 is linked to neoplasm.