
15 Utilizing Circulating Tumor Cells to Guide HER2-Directed Therapy in IHC/FISH-Negative HER2+ Metastatic Breast Cancer
Background The diagnosis of HER2-positive metastatic breast cancer (MBC) is complicated by tumor heterogeneity and temporal changes in HER2 expression. Circulating tumor cells (CTCs) serve as valuable noninvasive markers for HER2 expression when pathologic …