THYROPEROXIDASE IMMUNODETECTION FOR THE DIAGNOSIS OF MALIGNANCY ON FINE-NEEDLE ASPIRATION OF THYROID-NODULES

We have previously demonstrated that in 95.6% of malignant thyroid tum ors the enzyme thyroid peroxidase (TPO) presents antigenic changes det ectable by a monoclonal antibody termed MoAb47. The aim of this study was to investigate the interest of TPO immunodetection for the diagnos is of malignancy on fine-needle aspiration biopsy (FNAB) of thyroid no dules. The study was performed on 300 patients. Slides of FNAB aspirat e were air-dried acid stained by anti-TPO-MoAb47, According to the per centage of TPO-positive epithelial cells, patients were divided into t wo groups: benign (> 80%) and malignant (< 80%). In 279 cases addition al slides were available for Giemsa stain and standard cytology. All t he patients were operated on, and the final diagnosis was recorded as benign in 248 cases (183 macrofollicular nodules, 23 microfollicular a denomas, 18 atypical adenomas, 11 oncocytomas, 11 thyroiditis, 2 Grave s' disease) and malignant in 52 cases (44 papillary carcinomas and 8 f ollicular carcinomas). Samples from 215 of 248 benign nodules yielded 80% to 100% TPO positive cells, whereas samples from all malignant tum ors yielded less than 80% positive cells. The sensitivity of TPO stain ing for diagnosis of malignancy was thus 100%, its specificity 86.7%, and its overall accuracy 89%. With conventional cytology, sensitivity, specificity, and accuracy were 91.6%, 79.2%, and 81.0%, respectively. We conclude from this study that TPO staining with MoAb47 should beco me an essential adjunct in the preoperative cytologic diagnosis of thy roid nodules.