Phanop Limlunjakorn, M.D., Somboon Keelawat, M.D., F.R.C.Path. (Thailand), Andrey Bychkov, M.D., Ph.D.
Department of Pathology, Faculty of Medicine, Chulalongkorn University
Introduction: Fine-needle aspiration (FNA) cytology is a gold standard for preoperative evaluation of thyroid nodules. Recently introduced, the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has attempted to standardize reporting and cytological criteria in aspiration smears. This reporting format suggested six diagnostic categories, brieﬂ y deﬁ ned as follows: 1) non-diagnostic, 2) benign, 3) atypia of undetermined signiﬁ cance (AUS), 4) follicular neoplasm, 5) suspicious for malignancy, and 6) malignant. TBSRTC guides clinicians for further management and investigation. Previous Thai experience with thyroid FNA was reported in several local publications, and none of these employed TBSRTC. The aim of this study was to investigate the distribution of thyroid cytological diagnoses according to TBSRTC, and to correlate FNA ﬁ ndings with the results of the histopathological study.
Materials and Methods: We reviewed all of thyroid FNA reports in 2009-2015 performed at KCMH. The FNA results were classiﬁ ed according to TBSRTC. Histopathology reports for operated cases were used to correlate cytology and ﬁ nal histopathology.
Results: A total 2531 FNA of thyroid nodules from 1800 patients were reviewed. The number of thyroid FNA has grown over the years. The rate of the non-diagnostic, benign, AUS, follicular neoplasm, suspected for malignancy and malignant were 47.3%, 42.1%, 2.5%, 2.8%, 2.1% and 3.2% respectively. The proportion of non-diagnostic category is extremely high compared with the worldwide experience. Rate of malignancy for 433 operated thyroid nodules was 17%, 14%, 39%, 22%, 84% and 93% for categories 1 to 6, respectively.
Conclusion: TBSRTC is a reliable predictor of malignancy in thyroid FNA. The Bethesda system is useful as a standardized system for reporting thyroid cytopathology, improving communication between cytopathologists and clinicians, and inter-laboratory agreement, leading to more consistent management approaches. Additional efforts are needed to improve management of thyroid nodules in KCMH. There is a substantial proportion of undetermined cases (categories 3-5), which needs further stratiﬁ cation with ancillary techniques.