Analysis of Fine Needle Aspirations of the Thyroid: Cytological-Histopathological Correlation and Outcomes of the Bethesda System

Abstract

Objective: The Bethesda system is widely used to evaluate aspiration of thyroid nodules. The aim of the study is to evaluate the usability of the system by the correlation between cytology and final histopathology results and to review the literature.
 Material and Methods: Fine needle aspiration of thyroid nodules reported using Bethesda system were analyzed. Malignancy rates were calculated by the results of thyroidectomies. To analyze the power of the Bethesda system six distinct subgroups were designed. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were calculated separately in these subgroups. The data were analyzed using SPSS 20 for Windows.
 Results: The distribution of thyroid nodules according to the Bethesda was 2212 (33.5%), 3163 (47.9%), 720 (10.9%), 67 (1%), 361 (5.5%) and 75 (1.1%), respectively. Of 873 nodules that underwent thyroidectomy, 254 (29.9%) were diagnosed as malignant. The diagnostic categories according to thyroidectomies were 233 (26.7 %), 277 (31.7%), 137 (15.7%), 23 (2.6%), 163 (18.7%) and 40 (4.6%), respectively. The malignancy rates of each Bethesda category were 14.5%, 6.8%, 32.8%, 52.1%, 66.8% and 97.5%. The sensitivity, spesifity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of fine needle aspiration was calculated and ranged from 61.8% to 89.3%, 79.6% to 99.6%, 70.4% to 97.5%, 84.5% to 93.1% and 79.5% to 93.6%, respectively.
 Conclusion: The limitation of this study is that the B1 category is very high. However, since the data are evaluated by only one pathologist and it is one of the first three studies with the highest number of cases, it makes a significant contribution to the literature in terms of all categories except B1. The Bethesda system is a classification that provides the clinician with appropriate clinical follow-up and the accurate treatment approach, and a high interobserver agreement for pathologists.