ERBB4 and breast cancer: In BC, HER1, HER2, and HER3 exhibit a pro-carcinogenic effect (Hsu and Hung, 2016), whereas the role of HER4 is dual (Lucas et al., 2022), possibly due to the selective splicing of HER4 mRNA, which produces four variants: JM-a/CYT1, JM-a/CYT2, JM-b/CYT1, and JM-b/CYT2 (Veikkolainen et al., 2011).