Frequency of Deleterious Germline Variants in HER2-Low Breast Cancer Patients Using a Hereditary Multipanel Gene Testing.

HER2-Low is defined as low levels of HER2 expression, based on a score of 1+ on immunohistochemical (IHC) assay or as an IHC score of 2+ and negative results on in situ hybridization (ISH or FISH). They are a heterogeneous population of breast cancers that vary in prognosis and sensitivity to systemic treatments. The frequency and clinical characteristics of pathogenic germline variants (PGVs) in HER2-Low breast cancer (BC) patients is not defined.