The diagnostic value of fine needle aspiration cytology in the assessment of thyroid nodules: an 8-year analysis in Hormozgan

Thyroid nodules are common clinical problems, their importance being due to the possibility of malignancy. Fine needle aspiration cytology-FNAC is widely accepted as a simple, safe and accurate test in the assessment of nodular thyroid disease. Several studies based on different methodologies have reported different sensitivity, specificity, positive and negative predictive values and diagnostic accuracy for thyroid FNAC. In this retrospective study, 1397 FNAC cases (1242 female, 155 male, F/M=8) with an age range of 7-85 years, were reviewed for an 8-year duration in the pathology department of the Bandar-Abbas Medical School. The cytologic results were categorized in 5 groups: inadequate, suboptimal, benign, malignant and suspicious. In 101 cases (88 female, 13 male, F/M=7) with age range of 17-70 years, slides of thyroidectomy specimens were prepared. Evaluation of FNAC specimens, revealed 11.3% nondiagnostic cases(including inadequate 5.4% and suboptimal specimens 5.9%). Other cytologic groups were: benign- 75.2%, malignant- 3.8% and suspicious nodules- 9.7%. Final histopathologic diagnoses were benign in 65.3% and malignant in 34.7% of nodule specimens. The most common benign lesions were adenomatous and colloid goiter and the most common malignancy was papillary carcinoma. For evaluation of diagnostic value of thyroid FNAC, malignant and suspicious cases were considered as positive cytologic results and final malignant diagnoses (excluding occult papillary thyroid carcinoma) as positive histopathologic results. The sensitivity of thyroid FNAC was 91%, specificity 67%, positive and negative predictive values 58% and 94% respectively and the diagnostic accuracy 75%. FNAC has an acceptable diagnostic accuracy in the assessment of thyroid nodules and screening of patients for thyroidectomy but in areas with high prevalence of follicular lesions, because of the limitation of FNAC to differentiate follicular lesions, specificity and positive predictive value are decreased. FNAC however is useful only as an adjunct to clinical judgment and not as a replacement.