THYROID PEROXIDASE IMMUNODETECTION AS A TOOL TO ASSIST DIAGNOSIS OF THYROID-NODULES ON FINE-NEEDLE ASPIRATION BIOPSY

In a previous work we have reported the presence in 96.9% of malignant and 4.2% of benign thyroid tumors of an immunological abnormality of the enzyme thyroid peroxidase, impeding the fixation of the anti-thyro id peroxidase monoclonal antibody termed ''MoAb47''. The present study has been designed to establish the ability of thyroid peroxidase immu nodetection to assist the diagnosis of malignancy in fine-needle aspir ation of thyroid nodules. The fixation of anti-thyroid peroxidase mono clonal antibody was investigated by immunohistochemistry on fine-needl e aspirates of 150 surgically removed thyroid nodules (20 papillary ca rcinomas, five follicular carcinomas, 90 colloid adenomas, nine fetal adenoma, 13 atypical adenomas, five oncocytic adenomas, six Hashimoto' s thyroiditis and two Graves' disease). The percentage of positive cel ls has been compared to the final histological diagnosis. In samples f rom 113/125 benign nodules 80-100% cells presented a positive immunore action, whereas all samples from malignant tumors yielded less than 80 % positive cells. Benign nodules exhibiting less than 80% positive cel ls corresponded to three degenerative colloid nodules, five atypical f ollicular adenomas, two oncocytomas and two thyroiditis. According to results obtained in this series, with the value of 80% as the limit fo r discrimination between benign and highrisk nodules, the sensitivity of thyroid peroxidase staining for diagnosis of malignancy would be 10 0%, its specificity 90% and its overall accuracy 92%. Thyroid peroxida se staining with monoclonal antibody MoAb47 on fine-needle aspirates i s a useful adjunct to conventional cytology for the investigation of p atients with thyroid nodules.