ABSTRACT
Thyroid nodules are a common clinical problem and Fine Needle Aspiration [FNA] is the principal method used for preoperative diagnosis. This study was designed to evaluate the diagnostic accuracy of FNA for detection of malignancy in thyroid nodules. In this retrospective study, 1016 patients with thyroid nodule were evaluated over a six year period [1999-2005]. FNA was done for all of these patients by two expert pathologists. Thyroidectomy was performed on 104 patients and the cytologic and pathologic diagnoses were compared. For evaluation of diagnostic value of FNA, malignant and suspicious diagnoses of FNA were considered as positive cytologic results and the final malignant cases [excluding microscopic carcinoma] as positive pathologic results. In addition, risk of malignancy in thyroid nodules was calcuated based on the cytologic results documented in our patients. There were 884 females and 132 males [f/m: 7:1], with an age range of 9-81 years. The cytological results of 1016 specimens were as follows: 85% benign, 7% suspicious, 0.9% malignant and 7% inadequate. One hundred and four patients underwent surgery, [85 females and 19 males, f/m: 4.5:1], with an age range of 13-56 years. Preoperative cytologic results in this group were as follows: 62.5% benign, 35.5% suspicious and 2% malignant. Final pathologic results were 83.6% benign and 16.3% malignant. FNA sensitivity was 93.8%, specificity 72.7%, diagnostic accuracy 75.9%, positive predictive value 38.4% and negative predictive value 98.4%. False positive rate was 27%, and false negative rate 6%. Among patients with a suspicious cytology who were operated, malignancy in pathologic results was 35% [13 cases of 37 cases]. While the incidence of malignancy in thyroid nodules was 3.8% in all patients, this rate was 6% in solitary thyroid nodules and 2% in multinodular goiters. Because of its high sensitivity and low false negative results, FNA seems a reliable method for the diagnosis of cancer in thyroid nodules, a method however that is useful only as an adjunct to clinical judgment and not as a replacement