In the present study, we evaluated the protein expression of γ1-adaptin in breast cancer tissues by IHC, and found that γ1-adaptin expression is higher in breast cancer regions than in non-cancer regions, and that higher expression of γ1-adaptin is well associated with Ki-67, ER/PgR-negativity, HER2-positivity, and poor RFS. This evidence concerns the gene ERBB2 and cancer.