Thyroid peroxidase (TPO) is located on the apical free surface of thyroid epithelial cells and directly participates in the oxidation of iodine, iodization of tyrosine, and coupling of iodinated tyrosine in thyroid cyst cells. It is a key enzyme in the synthesis of thyroid hormones. High expression of TPO is observed in normal, proliferative, and most benign thyroid tissues, while significant reduction is observed in malignant thyroid tumors; In pathology, it mainly assists in the diagnosis of goiter and thyroid cancer, and is widely expressed in normal thyroid and benign thyroid lesions. The expression of thyroid cancer is reduced, but the specificity and sensitivity for distinguishing between benign and malignant thyroid tumors are not high.