INTRODUCTION: FNAB is considered the most reliable, safe, and cost-effective screening test for the diagnostic evaluation of thyroid nodules (TN), with sensitivity and specificity reported >90%. On the other hand, FNAB has the inherent and accepted problem of indeterminate cytology, which is neither strictly benign nor clearly indicative of malignancy, and the inclusion or exclusion of this category in statistical analyses calculation may cause a wide variation of diagnostic accuracy of cytology (Lewis et al, Thyroid 19, 2009). As additional problem, different approaches to FNAB of TN might potentially influence the prevalence rates of all cytological classes. PURPOSE: To evaluate the impact of different approaches to FNAB of TN on the distribution of cytological results, by comparing a large series of FNABs carried out in different institutions. SUBJECTS AND METHODS: During a 2-year period (from January 2008 to December 2009) a total of 3070 consecutive thyroid nodules (2720 patients) were submitted to ultrasound (US)-guided FNAB, in one Endocrinology Unit and 3 Surgery Units of the same metropolitan area. All samples were evaluated by the same pathologist (M.L.L.) and classified as nondiagnostic (THY 1), benign (THY 2), indeterminate (THY 3), suspicious of malignancy (THY 4) or malignant (THY 5). FNABs in 2 of the above units were carried out by experienced physicians who also followed a selective approach according to the recent USA and European guidelines (group A, n= 2327). FNABs in the other 2 units were performed by less experienced operators, who followed an unselective approach, aspirating most of the nodules including those without suspicious clinical and/or US features (group B, n= 743). RESULTS: A total of 2528 samples were adequate for cytological diagnosis. A significant higher prevalence of THY 3 (511/2028, 25.2% vs 52/500, 10.4%, p<0.0001) and THY 4-5 (188/2028, 9.3% vs 11/500, 2%, p<0.0001) and a significant lower prevalence of THY 2 (1329/2028, 65.5% vs 438/500, 87.6%, p<0.0001) were found in Group A vs Group B nodules, respectively. Moreover, the prevalence of inadequate samples was significantly (p<0.0001) higher in group B (243/743, 32.8%) vs group A nodules (299/2327, 12.8%), confirming the lower experience of the operators using unselective approach. CONCLUSIONS: This study confirms that a selective FNAB approach to thyroid nodules based on clinical and US criteria, as advised by the current guidelines, allows the identification of a higher proportion of suspicious or malignant thyroid tumors. However, selective approach also provided higher rate of indeterminate cytology, which may affect the diagnostic accuracy of the FNAB, depending on the inclusion or exclusion of THY 3 nodules. This phenomenon may have important consequences in the clinical management of TN and may limits comparison of results among different centers.
Different approaches to fine-needle aspiration biopsy of thyroid nodules affect the rate of benign, indeterminate and malignant cytology.
Boi F
;Tamponi E;Faa G;Mariotti S.
2010-01-01
Abstract
INTRODUCTION: FNAB is considered the most reliable, safe, and cost-effective screening test for the diagnostic evaluation of thyroid nodules (TN), with sensitivity and specificity reported >90%. On the other hand, FNAB has the inherent and accepted problem of indeterminate cytology, which is neither strictly benign nor clearly indicative of malignancy, and the inclusion or exclusion of this category in statistical analyses calculation may cause a wide variation of diagnostic accuracy of cytology (Lewis et al, Thyroid 19, 2009). As additional problem, different approaches to FNAB of TN might potentially influence the prevalence rates of all cytological classes. PURPOSE: To evaluate the impact of different approaches to FNAB of TN on the distribution of cytological results, by comparing a large series of FNABs carried out in different institutions. SUBJECTS AND METHODS: During a 2-year period (from January 2008 to December 2009) a total of 3070 consecutive thyroid nodules (2720 patients) were submitted to ultrasound (US)-guided FNAB, in one Endocrinology Unit and 3 Surgery Units of the same metropolitan area. All samples were evaluated by the same pathologist (M.L.L.) and classified as nondiagnostic (THY 1), benign (THY 2), indeterminate (THY 3), suspicious of malignancy (THY 4) or malignant (THY 5). FNABs in 2 of the above units were carried out by experienced physicians who also followed a selective approach according to the recent USA and European guidelines (group A, n= 2327). FNABs in the other 2 units were performed by less experienced operators, who followed an unselective approach, aspirating most of the nodules including those without suspicious clinical and/or US features (group B, n= 743). RESULTS: A total of 2528 samples were adequate for cytological diagnosis. A significant higher prevalence of THY 3 (511/2028, 25.2% vs 52/500, 10.4%, p<0.0001) and THY 4-5 (188/2028, 9.3% vs 11/500, 2%, p<0.0001) and a significant lower prevalence of THY 2 (1329/2028, 65.5% vs 438/500, 87.6%, p<0.0001) were found in Group A vs Group B nodules, respectively. Moreover, the prevalence of inadequate samples was significantly (p<0.0001) higher in group B (243/743, 32.8%) vs group A nodules (299/2327, 12.8%), confirming the lower experience of the operators using unselective approach. CONCLUSIONS: This study confirms that a selective FNAB approach to thyroid nodules based on clinical and US criteria, as advised by the current guidelines, allows the identification of a higher proportion of suspicious or malignant thyroid tumors. However, selective approach also provided higher rate of indeterminate cytology, which may affect the diagnostic accuracy of the FNAB, depending on the inclusion or exclusion of THY 3 nodules. This phenomenon may have important consequences in the clinical management of TN and may limits comparison of results among different centers.
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