As approvement of anti-HER2 ADCs drugs in treatment of breast cancer patients, the traditional negative expression of HER-2 has been classified as two subgroups, HER2-0 for tumors scored IHC 0 and HER2-low for tumors scored IHC 1 + or 2 + with a nonamplified FISH assay. Here, ERBB2 is linked to breast carcinoma.