Abstract
Objectives : To clarify a significance of “benign” in the Thyroid Bethesda System (TBS), we compared benign lesions based on the TBS and the Japanese Reporting System (JRS).
Study Design : We reviewed the aspiration cytology findings of 10333 thyroid nodules encountered in Kuma Hospital from January to December 2011.
Results : The incidence of “benign” was 73.0% according to the JRS and 67.8% according to the TBS. This difference was because cystic lesions without follicular cells (“cyst fluid”) were classified as “benign” according to the JRS and as “inadequate” according to the TBS. The re-aspiration rates were 1.6% according to both reporting systems. In most of the re-aspiration cases, the ultrasonographic findings were considered as “indeterminate” or “suspicious for malignancy” . The resection rates for “benign” nodules diagnosed according to the JRS and TBS and “cyst fluid” were 8.1%, 8.2% and 6.5%, respectively. The risk rates of malignancy in the three groups were 1.2%, 1.1% and 1.7%.
Conclusion : There were no significant differences in the incidences of re-aspiration rates, resection rates or risks of malignancy between “benign” lesions diagnosed by JRS and TBS. As the results were within the ranges recommended by the TBS, it is considered that the TBS can be accepted without any concerns in Japan. We recommend that cystic lesions without follicular cells be managed as “benign”.
