Evidence suggests that USP15 stabilizes oncoproteins by deubiquitination, thereby promoting proliferation in most cancers, including breast cancer, multiple myeloma, gastric cancer, glioblastoma, etc. However, some studies also point to USP15 acting as a negative regulator in certain tumor growth, which complicates the role of USP15 in tumors, suggesting that USP15 is a critical and promising target for tumor therapy. This evidence concerns the gene USP15 and breast cancer.