Rates of Malignancy in Cytology Indeterminate Thyroid Nodules: A Single Center Surgical Series.

BACKGROUND: Due to the high variability in malignancy rate among cytologically indeterminate thyroid nodules (Bethesda categories III-V), the American Thyroid Association recommends that each center define its own categorical cancer risk. OBJECTIVES: To assess cancer risk in patients with cytologically indeterminate thyroid nodules who were operated at our center. METHODS: In a retrospective study, we analyzed the pathology results of all the patients whose fine needle aspiration results showed Bethesda III-V cytology and who subsequently underwent total thyroidectomy or lobectomy from December 2013 to September 2017. RESULTS: We analyzed 56 patients with indeterminate cytology on fine needle aspiration. Twenty-nine (52%) were defined as Bethesda III, 19 (34%) Bethesda IV, and 8 (14%) Bethesda V category. Malignancy rates were 38%, 58%, and 100% for Bethesda categories III, IV, and V, respectively. Most malignancies in Bethesda categories III and IV were follicular in origin (follicular thyroid carcinoma and follicular type papillary thyroid carcinoma), while 100% of the patients with Bethesda category V were diagnosed with classical papillary thyroid carcinoma. No correlation was found between sonographic and cytological criteria of nodules with Bethesda categories III and IV and rates of malignancy. CONCLUSIONS: We found higher than expected rates of malignancy in indeterminate cytology. This finding reinforces the guidelines of the American Thyroid Association to establish local malignancy rates for thyroid nodules with indetermined cytology.

Thyroid malignancy rates according to the Bethesda reporting system in Israel - A multicenter study.

INTRODUCTION: The Bethesda System for Reporting Thyroid Cytopathology was developed in 2007 to facilitate an accurate, reproducible communication of thyroid fine-needle aspiration (FNA) interpretations between clinicians and cytopathologists and to serve as a guide for treatment. Based on large patient series, the system details the risk of malignancy for each category as well as a suggested management for each FNA result. Though this system has been widely adopted, there are only few studies to determine whether results are applicable for Israel. METHODS: A multicenter, retrospective analysis of medical charts of all patients who underwent thyroid surgery between January 1st, 2012 and December 31st, 2016 in four medical centers in Israel was performed. Data was analyzed for the overall risk of malignancy for the Bethesda system groups as well as comparison between the different laboratories performing the test. RESULTS: Records of 810 thyroidectomies in which preoperative cytological reports and final pathology were available and reviewed. The malignancy rates according to the Bethesda groups' I-VI for our cohort were: 27.8%, 17.6%, 41.4%, 41.4%, 86.9%, and 98.1% respectively. Similar results were seen when results were analyzed according to the different laboratories performing the tests. CONCLUSIONS: Post-surgical review of all Bethesda groups had higher malignancy rates than those reported in the original report. These results indicate a difference in the malignancy rates for the different Bethesda system groups in Israel compared to those reported. Physicians are encouraged to use data validated for their own country or patients' community in addition to published values.