Abstract
Objective : The aim of this study was to examine usefulness of CD26 as a marker to evaluate the grade of differentiation in thyroid cancer.
Study Design : Staining for dipeptidyl peptidase IV (CD26/DPPIV) was applied to fine needle aspiration smears obtained from thyroid tumors. The staining pattern could be divided into apical, diffuse, mixed, and dot patterns, and these patterns were evaluated in relation to the histological differentiation grades. We examined the cell morphology in detail in four cases of poorly differentiated carcinoma (PDC).
Results : The CD26 staining pattern in 100 cases of well- differentiated papillary carcinoma (WDPC) was as follows : apical 24%, diffuse 51%, and mixed 25%. In contrast, among 23 cases of poorly differentiated carcinoma (PDC), the apical, diffuse, mixed, and dot staining patterns were observed in 13.0%, 30.4%, 39.1%, and 17.4% of cases, respectively. The distribution of the CD26 staining pattern in cases of follicular carcinoma was approximately similar to that in cases of papillary carcinoma. The dot pattern was limited to one case of PDC. Definitive diagnosis of PDC on cytology was difficult.
Conclusion : Staining for CD26 is a simple and specific assay useful for the accurate diagnosis of thyroid tumors ; furthermore, it is also useful to evaluate the degree of differentiation of thyroid carcinoma.
