Fine needle aspiration cytology of nodular thyroid lesions: a 2-year experience of the Bethesda system for reporting thyroid cytopathology in a large regional and a university hospital, with histological correlation.

ABSTRACT

OBJECTIVE: Thyroid fine needle aspiration (FNA) contributes to the appropriate management of nodular thyroid lesions. The introduced categories in the Bethesda system for reporting thyroid cytopathology (TBSRTC) are associated with an implied cancer risk, providing a clinical management guideline. This study aims to evaluate the reproducibility of this implied risk and to compare the results from two different cytopathology departments. METHODS: Five hundred histologically confirmed FNAs, studied since the introduction of TBSRTC, were obtained from 4208 and 3587 FNAs performed in a large regional hospital in Herakleion, Crete (group A) and a university hospital in Athens (group B), respectively. Reports were issued according to TBSRTC. Aspirates were prepared with ThinPrep(®) and evaluated by two experienced cytopathologists. The reproducibility and accuracy were evaluated. RESULTS: The proportion test for suspicious for malignancy (SFM) and malignant (M) cytology reports (P < 0.0001), and the number of malignancies on histology (P < 0.0001), were significantly higher in group A than in group B, consistent with a higher incidence of thyroid carcinomas in southern Greece. Although the malignancy rates were higher in group A than in group B for all categories, except M (A, 99.3%; B, 100%), the difference was only significant for benign aspirates (P = 0.0303). Malignancy rates for all categories in group A were above the TBSRTC recommended range, but were consistent with an increased prevalence of malignancy in that centre, differences in reporting practice and the variable ranges reported in the literature. There was lower sensitivity (P = 0.019) and overall accuracy (P = 0.003) in group A relative to group B, but no difference in specificity. CONCLUSIONS: TBSRTC provides valuable information for the appropriate management of nodular thyroid lesions, both in a university and a large regional hospital.