Context: The diagnosis of FNA cytology of follicular variant papillary carcinoma is difficult and it is always a source of cytodiagnostic error of thyroid nodules.
Objective: This study was aimed to determine whether immunostaining expression pattern of CD44v6 and CK19 in thyroid aspirate with suspicious cytology is a useful ancillary technique for diagnosis of follicular variant papillary thyroid carcinoma and to assess its utility in differentiating follicular variant papillary carcinoma (FVPC) from other follicular thyroid lesions with cytomorphological overlapping.
Material and Method: This study was performed on FNA thyroid cytological smears of 47 cases with suspicious or indeterminate cytological diagnosis where the diagnosis of the corresponding surgical specimens was as following: Folli¬cular variant papillary carcinoma (FVPC) (18 cases), Classic papillary carcinoma (CPC) (12 cases), Follicular adenoma (FA) (8 case), follicular carcinoma (FC) (4 cases) and adenomatoid colloid goiter (5 cases). Four cases of colloid nodular goiter were used as control group. Using monoclonal antibody for detection CD44v6 and CK19, the immunostaining was performed on thyroid cytological smears and the paraffin blocks of its corresponding surgical specimens. The presence of membranous staining w as necessary to considered staining for CD44v6 as positive. The staining reaction of CK19 is scored according to the intensity and the extent of the cyto¬plasmic immunorcactivity as follow: 1+ (75% positively stained cells).