Anaplastic thyroid carcinoma. A clinical, histologic, and immunohistochemical study.

Twenty-six cases of anaplastic thyroid tumor were investigated and reclassified using immunoperoxidase techniques. Sections of the neoplasms were stained immunohistologically for the following thyroid associated antigens: (1) thyroglobulin, which shows a positive reaction with follicular cells of the thyroid; (2) calcitonin, which is positive in medullary carcinoma of the thyroid; and (3) leucocyte common antigen (LC), which identifies lymphomata and Factor VIII-related antigen for hemangioendothelioma. Using these methods, five cases were reclassified. Three cases were identified as lymphomata, one case was reclassified as medullary carcinoma of the thyroid, and one case was identified as hemangioendothelioma. Eleven cases were confirmed to be anaplastic carcinoma of the thyroid and ten cases were negative for all the antigens tested. There was a significant difference in the survival of the groups of patients mentioned above. Prognostic data support the suggestion that immunohistochemical methods should be used for the precise classification of anaplastic carcinoma. In this way, tumors such as malignant lymphoma and medullary carcinoma, which resemble anaplastic carcinoma histologically but have a better prognosis, can be identified. This is important for planning surgical procedures and choosing chemotherapy and/or radiotherapy.