PSA (prostate-specific antigen), a serine protease with chymotrypsin-like activity is the most useful tumor marker for prostate cancer screening, diagnosis, prognosis and monitoring. The identification of PSA in normal and tumoral mammary gland was regarded as a curiosity, but the confirmation of PSA expression in the mammary gland by others teams of researchers and the identification of specific mRNA in tumors with PSA immunoexpression initiated new perspectives for studies. The aim of this study was to examine the prevalence of PSA in breast cancers and to evaluate the correlations between PSA expression and some clinicopathological markers. We analyzed the expression of PSA in series of consecutive breast carcinomas by immunohistochemistry and correlated the PSA expression with the histological type and grade, nodal and metastasis status, estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR) and HER2/neu expression. PSA expression was observed in 44.5% of breast cancers, particularly in lobular types of carcinoma (p<0.0001). In univariate analysis, the expression of PSA was statistically correlated with AR (p<0.0001), PR (p=0.01) and inversely correlated with HER2/neu overexpression (p=0.008) and G3 (p=0.02). PSA did not significantly correlate with ER expression, lymph node and metastasis status. In multivariate analysis, PR was a moderate predictor (p=0.024) but the lobular type (p=0.000), AR (p=0.000), HER2/neu (p=0.002) and G3 (p=0.008) were strong predictors for PSA immunoexpression.