Comparison of the results of diagnosis and treatment between solid and cystic well-differentiated thyroid carcinomas

We assessed the accuracy of ultrasonography and fine-needle aspiration cytology (FNAC) in diagnosing cystic thyroid cancer and compared the results with solid thyroid cancer patients. We also compared the results of treatment between these patient groups. We retrospectively reviewed 1013 thyroid cancer patients who received treatment at Chang Gung Memorial Hospital. For this study, 910 cases of papillary or follicular thyroid carcinomas were considered eligible. Of these, 682 patients received preoperative high-resolution ultrasonographic and FNAC examinations. The nodules of 583 (85.5%) patients were diagnosed as solid masses, 80 (11.7%) as mixed masses, and 19 (2.8%) as cystic masses. Of the 19 patients with cystic thyroid carcinoma, only 4 papillary thyroid carcinomas were diagnosed by ultrasonography with FNAC as malignant before operation. Six patients presented as occult thyroid carcinomas with the tumor size less than 1 cm. Despite the low rate of accurate diagnosis for the cystic malignancy, clinical staging and the survival rates were not statistically different when they were compared with the other groups. In conclusion, low diagnostic rates were observed in well-differentiated thyroid cancer with prospective ultrasound-guided FNA when lesions were cystic or in mixed lesions. If the solid portion of the cystic masses is aspirated under ultrasound-guided FNA and cytology is performed after the centrifugation of the aspirated fluid, diagnostic accuracy may be improved.