We studied 24 selected breast tumors and 3 lymph nodes metastasis from patients with breast carcinoma. The biopsies were formalin-fixed, paraffin-embedded and sections were stained with haematoxylin-eosin. Additional sections from each case were immunostained for prostate specific antigen (PSA), using the EnVision technique. PSA was detected in 7% of normal breast tissues, in 54.5% of benign tumors and 46.5% of malignant tumors. The lesions with apocrine metaplasia were intense and constantly positive, the cystic dilated ducts and the areas with mastopathy were negative. Intense staining for PSA has been found in well-differentiated tumors, while the undifferentiated tumors were usually PSA-negative. The PSA-positivity in 2 of the 3 lymph nodes metastasis indicates that PSA immunoreactivity alone is not an individual prognostic indicator, but it correlates with the hormonal status of the female body. We discuss the results in terms of clinical implications of PSA immunoreactivity detection in mammary gland and other extra-prostatic sources.