Thyroglobulin in carcinoma of the thyroid: an immunohistochemical study.

To determine the value of thyroglobulin as an immunohistochemical marker for thyroid neoplasms, we studied 42 primary thyroid carcinomas, 38 metastatic carcinomas, and four sarcomas involving the thyroid gland. All follicular and papillary carcinomas, regardless of their morphologic variation, stained positively for thyroglobulin, whereas the medullary carcinomas, metastatic tumors, and sarcomas showed negative staining reactions. The only small-cell variant of follicular carcinoma and ten of 14 spindle and giant cell carcinomas showed the lowest thyroglobulin reactivity. It is concluded that immunohistochemical demonstration of thyroglobulin is a sensitive and specific method of identifying thyroid carcinomas of follicular cell origin.