Staining for dipeptidyl aminopeptidase IV activity in nodular thyroid diseases.

Objective: To determine the effectiveness of staining for dipeptidyl aminopeptidase IV (DAP IV) activity in thyroid nodular diseases.

Study Design: Imprint smears were made in 76 cases of papillary carcinoma, 10 of follicular carcinoma, 32 of follicular adenoma and 48 of adenomatous goiter after surgery, and staining for DAP IV activity was performed in all cases.

Results: All papillary carcinomas stained positively, and most adenomatous goiter cases were negative. Follicular carcinoma and follicular adenoma cases exhibited various degrees of positivity, though the former tended to be stained more than the latter. Of the total 166 cases of thyroid nodules, 53 showed negative staining; of those 53, all except 1 were benign. Follicular carcinoma cases that had vascular invasion tended to show a high DAP IV staining pattern, but no statistically significant difference between it and follicular carcinoma that did not show vascular invasion was found.

Conclusion: DAP IV activity staining might reveal malignant potential and could have some value in the preoperative diagnosis between thyroid nodular diseases. The DAP IV method is a reliable indicator of benign disease if negative results are obtained.