Although HER2-unamplified MBC patients do not regularly benefit from anti-HER2 target therapy, HER2 V777L mutation detected by next-generation sequencing from ctDNA may present as a predictive biomarker for anti-HER2-based strategy therapy in HER2-negative MBC patients.
This case report describes a young woman with metastatic breast cancer whose tumor was found to carry a HER2 L755S mutation, which is in the kinase domain of HER2.
Our study was designed to further analyze the existence of this cross-reaction and stress the need to exclude a metastatic breast cancer when dealing with EGFR L858R-positive cases.