Identification of unsuspected thyroid carcinoma using immunoperoxidase for thyroglobulin.

Two patients with poorly differentiated metastatic cancer were shown to have metastatic thyroid carcinoma. Each patient had poorly differentiated cancer and remaining thyroid tissue in the neck. The diagnosis was secured using the immunoperoxidase technique with an antibody against thyroglobulin. The proper evaluation of patients with carcinoma of unknown primary involves specific tissue identification using special techniques in pathology.