The aim of this study was to characterize better the relationship between the overexpression of ERBB2 oncogene and AP-2α transcription factor in primary breast tumors and to determine whether the expression level of the YY1 cofactor could play a role in the association between the expression of AP-2α and ERBB2. In this study, we first demonstrated that the expression of these proteins is positively correlated in breast cancer tissues. This evidence concerns the gene YY1 and breast cancer.