APPLICATION OF BETHESDA SYSTEM IN CYTOLOGICAL EVALUATION AND CORRELATION TO HISTOPATHOLOGY OF SOLITARY THYROID NODULE

Background: Thyroid nodules are common, and while most are benign, solitary thyroid nodule (STN) carry a risk of malignancy. Fine-needle aspiration cytology (FNAC) remains the cornerstone for preoperative evaluation. The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) was introduced to standardize reporting and improve communication, though indeterminate categories remain diagnostically challenging. Aim of the study: To assess the accuracy of application of Bethesda System for Reporting Thyroid Cytopathology in evaluating solitary thyroid nodules through fine-needle aspiration, and to correlate how its cytological classifications compare with final histopathological findings. Patients and methods: A cross-sectional study included 80 patients with STNs at Al-Kufa Training Center for Pathology between January 2025 to September 2025. FNAC samples and corresponding surgical specimens were histopathologically assessed as benign, malignant, or borderline. Associations between cytology, histology, and clinical variables were analyzed. Results: The study population comprised predominantly females (83.8%) with a mean age distribution peak of 20–40 years. Bethesda classification showed a significant association with histology and with benign vs malignancy status (p-value 0.001). Sensitivity, specificity, PPV, NPV, and accuracy were 97.3%, 65.2%, 81.8%, 93.8%, and 85.0%, respectively. Conclusion: The Bethesda system demonstrated high sensitivity and diagnostic accuracy in evaluating STNs, particularly in higher categories (IV–VI). It remains a reliable basis when combined with histopathology for guiding management decisions.