Breast Metastasis From Castrate-Resistant Prostatic Adenocarcinoma Mimicking as a Second Primary: A Case Report

The occurrence of breast metastasis from prostate carcinoma and primary breast carcinoma in men may cause a diagnostic dilemma. This report aims to present a patient diagnosed with metastatic castrate-resistant prostatic adenocarcinoma who developed breast metastasis mimicking as a second primary. A 57-year-old male patient presented with a breast mass while undergoing hormonal therapy for prostatic adenocarcinoma. The initial histopathologic diagnosis of the breast specimen was an infiltrating ductal breast carcinoma. The breast mass enlarged after four cycles of docetaxel. Immunostaining with prostate-specific antigen (PSA) and prostate-specific acid phosphatase (PSAP) was done on the breast specimen revealing a negative PSA and a moderately staining PSAP. These stains confirmed the diagnosis of a breast metastasis from prostatic adenocarcinoma. The differentiation between primary breast carcinoma and breast metastasis from prostate carcinoma is crucial. Hence, immunohistochemistry staining should be utilized for diagnosis and appropriate management.