Immunohistochemical detection of dipeptidyl peptidase IV (CD 26) in thyroid neoplasia using biotinylated tyramine amplification.

Differential diagnosis between malignant and benign thyroid tumors derived from follicular cells can pose certain difficulties in routine surgical pathology. The aim of the study was to evaluate dipeptidyl peptidase IV (DPP IV/CD 26) in differential diagnostics of thyroid lesions. DPP IV/CD 26 was evaluated in thyroid glands of 309 patients (261 females and 48 males, age range of patients 15-80 years). DPP IV/CD 26 was assessed in paraffin-embedded thyroid specimens immunohistochemically using commercially available antibody (Serotec) and biotinylated tyramine amplification kit (DAKO). Well-differentiated carcinoma revealed DPP IV/CD 26 positivity in 33 out of 42 cases (79%). Neither medullary nor insular carcinoma was DPPIV/CD 26 positive (only one case of each tested). DPPIV/CD 26 expression in isolated cells was seen in 18/261 (7%) benign disorders. The sensitivity of the method was 68%, the specificity was 94%, and the diagnostic accuracy was 91%, respectively, using 5% threshold of positive follicular cells. DPP IV/CD 26 can be assessed immunohistochemically using biotinylated tyramine amplification kit. DPP IV/CD 26 could be an adjunct in the thyroid gland differential diagnosis. However, DPP IV/CD 26 positivity is limited to the group of well-differentiated carcinomas, particularly papillary carcinoma. Furthermore, it is of limited value for follicular and oncocytic tumors.