Background. Morphological diagnostics of thyroid gland tumours faces certain differential diagnostic problems.
Extensive histological examination of the entire tumour is required for the final diagnosis of follicular and oncocytic
tumours. Thus, assessment of reliable definitive cytological and/or intraoperative histological diagnosis is not
possible. No marker of malignancy has been so far generally accepted in the thyroid tumour diagnosis. The aim of
the study was to evaluate membrane protease dipeptidyl peptidase IV(DPP IV) in the differential diagnosis of thyroid
Methods and Results. DPP IV was assessed cytochemically in 254 smears, histochemically in 314 cryostat sections,
and immunohistochemically in 309 paraffin-embedded sections obtained from the group of 336 patients. There were
283 females and 53 males with themean age of 48 years (range 15–80 years) in this series. Sensitivity of cytochemical
detection was 71 %, specificity was 96 %, and diagnostic accuracy was 93% using the 50 % threshold. Histochemically,
sensitivity was 71 %, specificity was 93 %, and diagnostic accuracy was 90 % using the 5% threshold. Using
the immunohistochemical assessment, sensitivity was 68 %, specificity was 94 %, and diagnostic accuracy was 91%
using the 5% threshold.
Conclusions. According to our results, DPP IV can be used as a marker of malignancy in well-differentiated
carcinomas of follicular cell origin, namely in papillary carcinoma. However, it is less reliable in follicular and
dipeptidyl peptidase IV, thyroid gland, thyroid tumours, thyroid diagnosis, cytochemistry, histochemistry,