MALIGNANCY MARKERS IN THE CYTOLOGICAL DIA GNOSIS OF THYROID-NODULES -DIPEPTIDYL-AMINOPEPTIDASE-IV (DAP-IV)

Dipeptidyl-aminopeptidase IV (DAP IV), an exopeptidase involved in T-c ell activation is absent from normal thyroid tissue bur highly express ed by malignant thyroid cells. It has been suggested to be a useful ad junct for the diagnosis of malignant thyroid tumors on fine needle asp irates (FNA). To assess this assumption DAP IV activity was demonstrat ed by histochemical staining on FNA performed on 102 thyroid nodules a t the time of surgery (60 macrofollicular adenomas, 15 microfollicular adenomas, 7 Hashimoto's thyroiditis, 3 Graves' disease, 13 papillary carcinomas and 4 follicular carcinomas). A staining score based on the percentage of positive epithelial cells and staining intensity was es tablished for each case and results were compared to histological diag nosis. Most cells in malignant rumors were deeply stained except in on e case of papillary carcinoma. Null or very low scores resulting from light or medium staining of less than 40 % of the cells were obtained in 78/85 benign nodules. In 6 macrofollicular adenomas and in I case o f thyroiditis staining score was as as high as in carcinomas. DAP IV s taining was correlated to malignancy in all follicular tumours (4 mali gnant tumours were positive and 15 benign were negative). The sensitiv ity for diagnosis of malignancy was 94.1 % and the specificity 91.7 %. This study brings confirmation that DAP IV activity detection could b e an useful adjunct to cytological examination Sor the distinction bet ween benign and malignant thyroid nodules, especially in cases of foll icular tumors.