A case of prostatic carcinoma metastatic to the orbit diagnosed by fine needle aspiration and immunoperoxidase staining for prostatic specific antigen.

A fine needle aspiration biopsy of the mass guided by computerized tomography was performed on a 65-year-old male with unilateral proptosis, inflammation, and diplopia in downgaze. Using an immunoperoxidase technique for prostatic specific antigen, the cytologic specimen stained positively. Subsequently, a needle biopsy of the prostate gland confirmed the presence of a moderately well-differentiated infiltrating carcinoma.