Immunohistochemical studies on thyroid peroxidase and thyroglobulin in 13 human thyroid tumors and 7 Graves' goiters.

Thyroid peroxidase (TPO) in 4 benign tumors, 9 malignant tumors and 7 Graves' goiters was examined both by biochemical methods (guaiacol and iodide oxidation assays) and histochemical methods (indirect immunofluorescence methods with polyclonal anti-TPO antibodies). The protein-based specific activity of TPO of Graves' goiters was comparable to or higher than that of normal thyroid tissues, while that of benign and malignant tumors were comparatively lower and variable. TPO was stained with the polyclonal anti-TPO antibodies in the cytoplasm of all benign adenomas, Graves' goiters and follicular carcinomas, but not of papillary carcinoma and metastatic cells. TPO staining markedly appeared in apical areas of Graves' goiters but was scarcely detected in the areas of other disordered thyroids. Polyclonal anti-thyroglobulin antibodies detected thyroglobulin in the follicular lumen of these diseased thyroids except in metastatic carcinoma cells.