Evaluation of Thyroid Fine Needle Aspiration Cytology
by the Bethesda Reporting System:
A Retrospective Analysis of Rates and Outcomes from
the King Chulalongkorn Memorial Hospital
Phanop Limlunjakorn MD*,
Somboon Keelawat MD*, Andrey Bychkov MD, PhD*
Affiliation :
* Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
Background : 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, briefly
defined as follows: 1) non-diagnostic, 2) benign, 3) atypia of undetermined significance (AUS), 4) follicular neoplasm, 5)
suspicious for malignancy, and 6) malignant. Previous experience with thyroid FNA from Thailand was reported in several
local publications, and none of these employed TBSRTC.
Objective : To investigate the distribution of thyroid cytological diagnoses according to TBSRTC, to correlate FNA findings
with the results of the histopathological examination, and to compare our results with available studies from Thailand.
Material and Method: We reviewed all thyroid FNA reports between 2009 and 2015 performed at the KCMH. The FNA
results were classified according to TBSRTC. Histopathology reports for operated cases were used to correlate cytology and
final histopathology.
Results : Two thousand seven hundred sixty two FNA of thyroid nodules from 2,004 patients were reviewed. The rate of non-
diagnostic, benign, AUS, follicular neoplasm, suspected for malignancy, and malignant cases was 47.6%, 40.8%, 3.9%,
2.6%, 1.9%, and 3.2% respectively. Very high rate of non-diagnostic samples was likely attributed to performer’s skills, high
prevalence of cystic nodules, and variations in microscopic interpretation. Malignancy rate in 457 operated thyroid nodules
was 19.2%, 14%, 37.9%, 20.9%, 81.5%, and 93.6% for categories 1 to 6, respectively.
Conclusion : The Bethesda system is recommended as a uniform system for reporting thyroid cytopathology, facilitating
communication between pathologists and clinicians, leading to more consistent management algorithms. Additional efforts
are needed to reduce the rate of non-diagnostic thyroid biopsies in the KCMH. There is substantial proportion of undeter-
mined nodules (categories 3 to 5) that needs further stratification with ancillary techniques.
Keywords : Thyroid nodule, Thyroid cancer, Fine-needle aspiration, Cytology, The Bethesda system for reporting thyroid
cytopathology, Risk of malignancy
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