Cystic change in thyroid cancer

Background: To determine the incidence of cystic change of thyroid cancer detected by ultrasonography and to compare the diagnostic accuracy of fine-needle aspiration cytology (FNAC) postultrasonography in solid and cystic thyroid nodules. Methods: This retrospective study collected data for 6219 patients with thyroid nodules. Mean patient age was 49.7 ± 13.6 years. Of these 6219 patients, 1983 had cystic changes of thyroid nodules and 4236 had solid masses as detected by ultrasonography. Following FNAC, 506 of the patients with solid masses (11.9%) underwent surgical treatment, compared with 143 of those with cystic change of thyroid masses (7.2%). Results: Of the 649 nodules treated surgically in the solid and cystic change groups, 29.8% (151/506) and 9.1% (13/143) were malignant, respectively. Overall, after surgical treatment, 0.65% of cystic changes to thyroid lesions were diagnosed as thyroid cancer. Diagnostic accuracy of FNAC in cystic changes of the thyroid masses after ultrasonographic examination resembled that in solid thyroid nodules. Conclusions: Cystic changes of thyroid masses are common. Positive predictive value in diagnosing papillary carcinoma of thyroid masses with cystic changes is high. Notably, preoperative accurate diagnosis is difficult.