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Background: Hürthle cell-rich nodules (HCNs) encompass non-neoplastic to malignant lesions. There is paucity of literature on the frequency distribution of HCNs among Bethesda categories, histologic follow-up, risk of malignancy (ROM), and risk of neoplasia (RON). The objective of this retrospective, multi-institutional study was to determine the prevalence of the cytologic diagnostic category and surgical outcomes of patients with HCN., Methods: Nine tertiary health centers representing 6 Asian countries participated. Cases were retrieved from respective databases. The Bethesda System for Reporting Thyroid Cytopathology was used. Cytology results were correlated with surgical diagnoses., Results: Of 42,190 thyroid aspirates retrieved, 760 (1.8%) had a Hürthle cell predominance. Most (61%) were categorized as atypia of undetermined significance/follicular lesion of undetermined significance, Hürthle cell type" (AUS-H); 35% were categorized as follicular neoplasm, Hürthle cell type (FN-H); and 4% were categorized as suspicious for malignancy (SFM). Histologic follow-up was available for 288 aspirates (38%). Most were benign on resection (66%), and the most common histologic diagnosis was Hürthle cell adenoma (28.5%). The ROM for AUS-H, FN-H, and SFM, as calculated on resected nodules, was 32%, 31%, and 71%, respectively; and the RON was 47%, 81%, and 77%, respectively. The 5 institutions that had an AUS-H:HCN ratio below 0.5 diagnosed HCN less frequently as AUS-H than as FN-H., Conclusions: This is the largest, contemporary, multi-institutional series of HCNs with surgical follow-up. Although there was wide interinstitutional variation in prevalence and surgical outcomes, there was no significant difference in the ROM among institutions. The categories AUS-H and FN-H had a similar ROM for resected nodules., (© 2019 American Cancer Society.)

Fine needle aspiration (FNA) has become a major diagnostic triage for clinical management of patients with a thyroid mass. Diagnostic accuracy of this procedure can be evaluated by cyto-histologic correlation. Out of 1,761 fine needle aspirates of thyroid glands performed from January 1996 to December 1999, 230 satisfactory specimens contained respective histologic correlates. Using histologic diagnoses as the gold standard, the overall accuracy, sensitivity and specificity for cytologic diagnoses of thyroid neoplasm were 90.4 per cent, 85.7 per cent, and 92.5 per cent respectively. The positive predictive value for diagnosing thyroid neoplasm was 83.3 per cent while the negative predictive value was 93.7 per cent. The common pairs of cyto-histological diagnostic discrepancy included adenomatous goiter vs follicular neoplasm, adenomatous goiter vs papillary carcinoma, and thyroiditis vs follicular neoplasm. In conclusion, FNA is a rapid, reliable and safe diagnostic tool to distinguish non-neoplastic from neoplastic lesions in patients with thyroid masses.