Patients with advanced HER2-positive breast cancer typically face a poor prognosis and require continuous anti-HER2 therapy from an early stage to maximize survival benefits.24 The heterogeneity of HER2 expression in breast cancer necessitates re-biopsies of recurrent or metastatic sites to accurately identify the cancer subtype, as recommended by current guidelines.25-28 However, the practical application of re-biopsy in clinical settings is often constrained due to various factors. This evidence concerns the gene ERBB2 and breast cancer.