Godoy-Ortiz, AnaAlba-Bernal, AlfonsoPascual, JavierComino-Méndez, IñakiAlba, Emilio2024-02-272024-02-272022-01-242072-6694http://hdl.handle.net/10668/20870http://hdl.handle.net/20.500.12105/18586Invasive breast cancer (BC) is the most common cancer in women with a slightly increasing yearly incidence. BC immunohistochemical characterisation is a crucial tool to define the intrinsic nature of each tumour and personalise BC patients' clinical management. In this regard, the characterisation of human epidermal growth factor receptor 2 (HER2) status guides physicians to treat with therapies tailored to this membrane receptor. Standardly, a tumour solid biopsy is therefore required, which is an invasive procedure and has difficulties to provide the complete molecular picture of the tumour. To complement these standard-of-care approaches, liquid biopsy is a validated methodology to obtain circulating tumour components such as circulating tumour DNA (ctDNA) and circulating tumour cells (CTCs) from body fluids in an easy-to-perform minimal-invasive manner. However, its clinical validity in cancer is still to be demonstrated. This review focusses on the utilisation of both ctDNA and CTCs in early and metastatic HER2-positive BC tumours. We discuss recently published studies deciphering the capacity of liquid biopsy to determine the response to neoadjuvant and adjuvant therapies as well as to predict patients' outcomes.engVoRhttp://creativecommons.org/licenses/by/4.0/HER2-positive breast cancercirculating-tumour DNAcirculating-tumour cellsearly breast cancerliquid biopsymetastatic breast cancerAttribution 4.0 International3515885514310.3390/cancers14030587Cancersopen access