BACKGROUND: S Phase Kinase Associated Protein 2 (Skp2), an F-box protein necessary for DNA replication, has recently been demonstrated to be an oncogene. The purpose of this study was to examine the Skp2 expression and to investigate its association with expressions of estrogen receptor (ER), androgen receptor (AR) and HER-2, as well as clinicopathological variables including tumor recurrence. METHODS: The expressions of Skp2, ER and AR were examined by immunohistochemistry and HER-2 amplification by chromogenic in situ hybridization (CISH) in 117 cases of breast carcinoma. RESULTS: Skp2 was expressed in 26 patients (22.2%) and was significantly correlated with tumor type (p=0.031), tumor grade (p=0.017) and ER expression (p=0.038). Twenty four (20.5%) of 117 patients had a tumor recurrence, and 6 patients (5.1%) died of multifocal metastases. Tumor recurrence was significantly correlated with histological grade (p=0.041) and lymph node status (p<0.001). CONCLUSIONS: Although Skp2 expression was statistically insignificant in association with tumor recurrence, it might be useful as a biologic predictor in breast cancer. The simple and reliable immunohistochemical assay presented in this study can be a routine part of breast cancer evaluation and may influence patient management.