Reproducibility of "The Bethesda System for Reporting Thyroid Cytopathology:" A Retrospective Analysis of 107 Patients

Abstract

Objectives: Fine-needle aspiration cytology (FNAC) has emerged as an indispensable tool to discriminate thyroid lesions into benign or malignant for appropriate management. The need for simplicity of communication and standardization of terminology for thyroid FNAC reporting led to introduction of "The Bethesda system for reporting Thyroid Cytopathology" (TBSRTC) in a conference held at the National Cancer Institute in 2007. This study aims at establishing the reproducibility of TBSRTC for diagnosing thyroid lesions.

Materials and methods: The present study comprised thyroid FNAC from 107 patients retrospectively over a period of 1.5 year (June 2013 to December 2014), which were reviewed by two trained cytopathologists and re-categorized according to TBSRTC. The interobserver variation and reproducibility of the reporting system was statistically assessed using Cohen's kappa.

Results: The cytopathologists were in agreement in 98 out of 107 cases (91.5%). Maximum concordance was noted in benign category (91 of 96 cases; 92.85%), followed by 2 cases each in nondiagnostic/unsatisfactory (ND/US) and follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) category (2.04% each) and 1 case each in atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), suspicious for malignancy (SUS), and malignant category (1.02% each). The highest diagnostic disagreement was noted among ND/US and benign and benign and FN/SFN categories.

Conclusion: The utilization of TBSRTC for reporting thyroid cytology should be promoted in our country because it provides a homogeneous, standardized, and unanimous terminology for cytological diagnosis of thyroid lesions. The present study could substantiate the diagnostic reproducibility of this system.

Keywords: Bethesda System; fine-needle aspiration cytology; reproducibility; thyroid.

Figure 1

(a) FNA smear showing presence of scattered macrophages in a background of abundant colloid mistaken as tissue fluid by one of the observers and was diagnosed as ND/US category (Giemsa stain, ×400). (b) FNA smear showing clusters of thyroid follicular cells with nuclear atypia in the background of colloid. This atypia was attributed to repair by one of the observers and as focal atypia by the other (Giemsa stain, ×400). (c) FNA smear showing follicular thyroid cells arranged in microfollicles (Giemsa stain, ×100). (d) FNA smear showing syncytial clusters of thyroid follicular cells with fire flares (arrows) (Giemsa stain, ×400)

Figure 2

(a) FNA smear showing moderate cellularity comprising scattered cells with atypia (arrows) suggesting malignancy (Giemsa stain, ×100). (b) FNA smear showing high cellularity comprising bizarre cells and microfollicular arrangement (arrow) favoring malignancy (Giemsa stain, ×400)