Sonography and fine-needle aspiration biopsy in the diagnosis of benign versus malignant nodules in patients with autoimmune thyroiditis

Purpose. To correlate sonographic (US) characteristics and results of fine-needle aspiration biopsy (FNAB) of thyroid nodules in autoimmune thyroiditis (AT) with surgical pathological findings. Method. Forty AT patients with 40 nodular lesions were analyzed retrospectively. Five sonographic characteristics were recorded for each nodule: diameter, echogenicity, microcalcification, halo sign, and margin. Preoperative sonograms and FNAB results were compared with postoperative histopathological findings. Result. Twenty-four of the 40 nodules were malignant, including 20 papillary carcinomas, 3 follicular carcinomas, and 1 medullary carcinoma. Of the 16 benign nodules, 8 were nodular hyperplasia, 6 lymphocytic thyroiditis, and 1 each follicular adenoma and Hurthle cell adenoma. The only US parameter that was significant in malignant vs. benign nodules was the presence of poorly defined margins. Based on preoperative cytology, 22 of the 23 malignant nodules were correctly diagnosed, and 10 of the 14 benign nodules were correctly identified. The positive predictive value was 78.6%, and the negative predictive value was 93.7%. Conclusion. No single US parameter can predict thyroid malignancy in patients with AT. A combination of US and FNAB provides the most sensitive and specific approach available preoperatively.