ERBB2 and breast cancer: Recently, FGFR4 overexpression and hotspot mutations have been associated with metastases and endocrine resistance in lobular metastatic BC [96], and a recent study suggested that FGFR4 promotes the transition from a more differentiated luminal phenotype to a highly proliferative and metastatic, endocrine-resistant, HER2-enriched subtype [97].