Immunohistological differentiation of benign thyroid follicular cell tumors from malignant ones: usefulness of anti-peroxidase and JT-95 antibodies.

An immunohistological investigation using anti-thyroid peroxidase (PO) and JT-95 (JT) antibodies was conducted on surgical specimens of papillary carcinoma (n = 12), follicular carcinoma (n = 8), follicular adenoma with prominent papillary structure (n = 12), follicular adenoma (n = 8) and adenomatous goiter (n = 8). In benign lesions, follicle-forming and papillae-forming epithelia showed positive staining with anti-PO antibody. In 26 of 28 benign lesions, PO-positive areas covered 50% or more of the cut surface area of the lesions. However in carcinomas, PO-positive areas were non-existent (13/20) or only focal (7/20) and the papillae did not stain. The incidence of JT-positive cases was higher in papillary carcinomas (12/12) than in other lesions (13/36). JT-positive areas were much wider than PO-positive areas in papillary carcinomas, whereas in benign lesions, PO-positive areas were wider than or at least roughly equal to, JT-positive areas. Follicular carcinomas did not stain or stained only focally with these antibodies. In conclusion, these two antibodies seem useful in differentiating benign from malignant follicular cell tumors.