Fine Needle Aspiration Cytology of Thyroid Follicular Neoplasm: Cytohistologic Correlation and Accuracy

Background This study evaluated the accuracy of fine needle aspiration cytology (FNAC) in cases of follicular neoplasm (FN) on the basis of histologic diagnosis, and reviewed the cytologic findings of FN according to the FNAC. Methods Among the 66 cases diagnosed with thyroid FN by FNAC during the 7-year period from 2003 to 2009, 36 cases that had undergone thyroid surgery were available for review. Cytologic diagnosis was compared with the histologic diagnosis of each case. Results Among the 36 cases with a cytologic diagnosis of thyroid FN, histologic diagnosis was as follows: 20 follicular adenomas (55.6%), 3 Hurthle cell adenomas (8.3%), 2 follicular carcinomas (5.6%), 8 nodular goiters (22.2%), 2 papillary carcinomas (5.6%), and 1 Hashimoto's thyroiditis (2.8%), resulting in a diagnostic accuracy of FNAC for thyroid FN of 69.5%. Conclusions This study shows that FNAC for thyroid FN is a useful primary screening method because when FN is diagnosed by FNAC, the rate of FN histologic diagnosis is relatively high, however, adequate sampling and experience is a prerequisite for this procedure.