ERBB2 and cancer: For a long time, the overexpression of HER2 by tumor cells was considered a predictor of a poor prognosis, until HER2-targeted therapy was introduced, starting with trastuzumab, which revolutionized the entire field of treatment for HER2-positive cancers and changed their prognosis, with the overexpression of HER2 becoming correlated with increased survival and better outcomes.