IMMUNOHISTOCHEMICAL DEMONSTRATION OF THYROID PEROXIDASE (TPO) IN HUMAN THYROID TISSUES FROM VARIOUS THYROID-DISEASES

Human thyroid peroxidase (hTPO) was detected immunohistochemically in 61 normal, benign and malignant thyroid tissues with a monoclonal anti body (38E) against hTPO using paraffin-embedded sections. Thyroid pero xidase was expressed intensely not only in tissues from Graves disease and hyperfunctioning adenomas, but also in those from carcinomas, ade nomas and Hashimoto's thyroiditis. The staining pattern of TPO in the follicular cells was a diffuse and fine granular one in the normal thy roids, Graves' thyroids and adenomas, bur abnormal coarse granular dep osits of TPO were characteristically identified in most of the papilla ry carcinomas and Hashimoto's thyroiditis. These coarse granular depos its of TPO suggested that qualitative or structural changes in the TPO molecule are present in carcinomas and Hashmoto's thyroiditis. Conseq uently, these qualitative changes in TPO may be responsible for the la ck of biochemically measured TPO activity in these diseases. This find ing may also be useful in distinguishing between benign and malignant thyroid tumors.