Thyroid Follicular Neoplasms Diagnosed by High-Resolution Ultrasonography with Fine Needle Aspiration Cytology

To investigate the final results of cases with preoperative diagnoses of thyroid follicular neoplasms by fine needle aspiration cytology (FNAC). A retrospective review of 6,499 patients who received thyroid ultrasonography with FNAC at Chang Gung Memorial Hospital. Among 6,499 patients, 209 (3.2%) were diagnosed by FNAC as having follicular neoplasms, of which 84 received surgical treatment. Eighty-two of the 84 cases had a frozen section prepared during the operation. Thyroid malignancy was confirmed histopathologically in 164 cases. Among 84 thyroid follicular neoplasm patients, 21 cases were diagnosed as malignant tumors, including papillary thyroid carcinoma, follicular thyroid carcinoma, medullary thyroid carcinoma and Hürthle's cell carcinoma. Ultrasonography on these 21 patients revealed that 16 cases (76.2%) had low echo density in the thyroid nodule. The percentage was statistically significantly different from that in benign cases, 23.8% (P < .05). A higher incidence of malignancy was found in males, but the data did not reach statistical significance (P = .0586). Most of the follicular neoplasms revealed by FNAC were benign lesions. Low echo density on ultrasonography and male sex carried a higher risk of malignancy.