ERBB2 and breast cancer: Furthermore, a rare HER‐2 variant Ile654Val is also associated with an increased familial breast cancer risk, which revealed an oncogenic role for carriers of the heterozygous Val654 allele (OR = 2.56, 95% CI = 1.08–6.08, P = 0.028) 81, meanwhile, it is linked with the more frequent Val655 to form two consecutive valines instead of two isoleucine residues 81.