MUC4 and breast cancer: From the above, MUC4 is known to be an active player in breast cancer metastasis and its deregulation has been implicated in gastric adenocarcinomas through the activation of ERBB2/HER2 and ERBB3/HER3 receptor kinases (Dreyer et al., 2021) (Funes et al., 2006) (Senapati et al., 2008).