Antibody to thyroglobulin has been shown to be useful in positive identification of thyroid carcinomas of the papillary and follicular types. Demonstration of thyroglobulin in a metastatic lesion establishes the thyroid origin of the tumor. Adenocarcinomas of non-thyroidal origin are not reactive. Clone 2H11+6E1 cocktail is especially designed for sensitive detection of thyroglobulin. It stains thyroglobulin in follicular epithelial cells as well as colloid tissue.