Publication:

Diagnostic accuracy of fine needle aspiration cytology for thyroid nodules under the 2023 Bethesda system: a retrospective analysis with future perspectives on artificial intelligence and molecular integration

Background Thyroid swellings are common clinical presentations in ENT and pose diagnostic challenges in differentiating benign from malignant lesions through clinical and ultrasonographic evaluation alone. FNAC offers a minimally invasive, rapid, cost-effective preoperative tool, though it is limited by an inability to differentiate certain indeterminate categories, such as follicular adenoma from follicular carcinoma. Modern adjuncts, including artificial intelligence (AI) and molecular testing, are increasingly explored to bridge these diagnostic gaps.

Methods This retrospective study was conducted in the Department of ENT, Father Muller Medical College, Mangalore, Karnataka, India between 1st October 2023 and 31st October 2025, involving 40 patients who presented with thyroid swellings and underwent preoperative FNAC followed by total thyroidectomy. Cytological results were classified utilizing the updated 2023 (3rd Edition) Bethesda system for reporting thyroid cytopathology. The FNAC findings were correlated with postoperative histopathological reports to determine sensitivity, specificity, predictive values, and accuracy.

Results Out of 40 thyroid swellings, Colloid nodular goitre was the most frequent condition on fine needle aspiration cytology (FNAC) (72.5%). Under the updated 2023 Bethesda system, 80% of cases were categorized as benign (Category II), with 5% demonstrating atypia of undetermined significance (AUS) (category III). Histopathology confirmed colloid nodular goitre in 60% and malignancy in 5% of cases. FNAC-histopathology correlation showed high concordance, demonstrating excellent diagnostic accuracy for benign and malignant lesions, with a sensitivity of 100%, specificity of 88.89%, positive predictive value of 96.88%, negative predictive value of 100%, and an overall diagnostic accuracy of 97.5%.

Conclusions FNAC is an essential first-line diagnostic tool for the preoperative evaluation of thyroid swellings, guiding surgical planning with high sensitivity and specificity. However, isolated false-positive interpretations highlight the inherent limitations of standard cytomorphology, underscoring the future necessity of integrating emerging molecular classifiers and AI-driven digital pathology to optimize the management of indeterminate nodules.