Diagnostic accuracy of fine needle aspiration cytology in thyroid lesions

Abstract

Purpose: Evaluation of accuracy of fine needle aspiration cytology (FNAC) in the diagnosis of different thyroid lesions.

Patients and methods: This is a retrospective study of 296 diagnosed cases of thyroid nodules referred to cytology unit, pathology department, NCI, who underwent FNAC for diagnosis. The results were categorized according to the recent Bethesda classification into: insufficient for diagnosis, benign, atypical follicular lesion of undetermined significance, follicular neoplasm, suspicious for malignancy, and malignant sampling. The final histologic diagnosis and/or clinico-radiologic follow-up assessment for non-neoplastic lesions were considered the gold standard.

Results: The study included 296 cases presented with thyroid nodules who underwent diagnostic thyroid FNAC. Female to male ratio was 5.2:1, and the median age was 44years. Ninety-eight cases (33.1%) were diagnosed as benign, 40 cases (13.5%) as follicular lesion of undetermined significance, 49 cases (16.5%) as follicular neoplasm, 30 cases (10.1%) as suspicious for malignancy, 58 cases (19.5%) as malignant, and 21 cases (7.1%) as unsatisfactory. Nodular hyperplasia represented the majority of benign cases (89.8%), while papillary carcinoma was the most frequent malignant lesion (72.4%). Cytologic diagnoses were compared with their corresponding final histologic ones. FNAC achieved a sensitivity of 92.8, a specificity of 94.2%, a positive predictive value of 94.9%, a negative predictive value of 91.8%, a false positive rate of 7.2%, a false negative rate of 5.8%, and a total accuracy of 93.6%.

Conclusion: FNA cytology is a sensitive, specific, and accurate initial diagnostic test for the evaluation of patients with thyroid swellings.