Rates of thyroid malignancy by FNA diagnostic category

Abstract

BackgroundFine needle aspiration (FNA) of thyroid nodules is a cornerstone of surgical decision making in thyroid cancer. The most widely utilized system for reporting thyroid FNA results is the Bethesda System, which includes predicted malignancy rates for each FNA category. To date there have been few studies to determine whether these predictions are widely applicable.MethodsAll thyroid FNA results at the Queen Elizabeth II Health Science Centre from 2006–2010 were included in this study. The results were tabulated by FNA category and the health records were reviewed to determine whether the patient went on to have surgery and the result of surgical histopathology. Rates of malignancy were calculated and compared to published values.ResultsA total of 1491 thyroid FNAs were included in the study, representing 1117 individual patients with available health records. The majority of these FNAs were Benign, but the proportion of Unsatisfactory FNAs was higher than predicted while Malignant and Suspicious for Malignancy were lower than predicted. Surgery was performed on 388 patients and 110 were positive for malignancy (28%). The malignancy rate for each FNA category was higher than predicted based on literature values.ConclusionsThe proportions of FNA diagnoses and the rates of malignancy for each FNA category at our institution were not consistent with predicted values. It is important for clinicians to base their surgical recommendations on institution specific malignancy rates, not solely on literature values.

Risk of malignancy for each Bethesda class in pediatric thyroid nodules

“…In accordance with the findings in this study, others have also found a high malignancy risk in pediatric BIV and BV nodules, 58 per cent and 100 per cent, respectively [10]. In comparison, adult BIV and BV lesions carry a malignancy risk of 20-36 per cent and 60-94 per cent, respectively [6,[11][12][13][14][15][16][17][18]. BVI nodules seem to be at almost 100 per cent risk of malignancy in children as well as in adults [11][12][13][14][15][16][17][18].…”

“…In comparison, adult BIV and BV lesions carry a malignancy risk of 20-36 per cent and 60-94 per cent, respectively [6,[11][12][13][14][15][16][17][18]. BVI nodules seem to be at almost 100 per cent risk of malignancy in children as well as in adults [11][12][13][14][15][16][17][18]. Most agree that the appropriate management for BVI nodules N1 cm in size is total thyroidectomy although the benefit of prophylactic central lymph node dissection is under debate [7,19].…”

“…Total ITC PTC FTC FA CN I 3 3 II 9 2 7 III 9 1 1 2 5 IV 4 2 2 V 3 1 1 1 VI 3 3 Total 31 2 7 3 4 15 ITC; insular thyroid cancer, PTC; papillary thyroid cancer, FTC, follicular thyroid cancer, FA; follicular adenoma, CN; colloid nodule. carcinoma, may therefore have a much higher yield to confirm cancer than in adult BIV nodules, where less than 15 per cent will be papillary thyroid cancers [11][12][13][14][15][16][17][18]. The diagnostic dilemma of BIII nodules in adults seems to be equally challenging in pediatric patients with a malignancy risk of around 18 per cent.…”

The Australian experience with the Bethesda classification system for thyroid fine needle aspiration biopsies

“…However, like all grading systems it is subject to interobserver variability and there have been significant discrepancies in the literature concerning the risk of malignancy in individual diagnostic categories, particularly for those lesions classified as Bethesda 3 (atypia of undetermined significance/follicular lesion of undetermined significance) and Bethesda 4 (suspicious for a follicular neoplasm), summarised in Table 2. 3,[7][8][9][10][11][12][13][14] For example, the reported risk of malignancy in Bethesda 3 nodules has ranged from 6% to 50%. 8,10 Furthermore, many of the cohorts from which the risks of malignancy (and therefore the standardised treatment recommendations) were derived were retrospectively accrued series based on re-examination by subspecialist endocrine cytopathologists.…”

“…3,[8][9][10][11] Other large validation cohorts were from the databases of surgical units and subject to a significant referral bias towards patients considered at high clinical risk of malignancy and therefore surgical referral. 12,14 To our knowledge there have been no large series detailing the risk of malignancy for the individual Bethesda categories in the Australian population. As a result, the published risks of malignancy for the different Bethesda categories may not represent the actual risk encountered in community based Australian practice.…”