Extraocular muscle metastasis 16 years following primary prostate carcinoma

An 83-year-old man with a history of localized prostate carcinoma treated 1 6 years prior with transurethral partial prostatectomy and radioactive seed implants presented with a 2-month history of right globe proptosis. Comput ed tomography demonstrated a right medial rectus mass. Serum prostate speci fic antigen (PSA) level was normal. Tumor biopsy revealed poorly differenti ated carcinoma with diffuse staining of tumor cells with PSA and prostatic acid phosphatase. This case demonstrates that prostate carcinoma may metast asize to an extraocular muscle many years after treatment of the primary tu mor and may not be accompanied by elevated serum PSA. Immunohistochemical s tains are helpful in establishing the diagnosis.