A 61-year-old black man presented with metastases to the right groin 5 years after 125iodine treatment for a well differentiated primary prostatic adenocarcinoma. Medium sized veins within and immediately adjacent to the neoplasm showed marked mural thickening due to hypertrophy and hyperplasia of the inner circular and outer longitudinal muscles. There was no histological evidence of radiation effect in the stroma or in the tumor cells. We could find no report in the literature of such changes associated with metastatic carcinoma.