Predictive Factors of Malignancy in Thyroid Nodules with Repeatedly Nondiagnostic Cytology (Bethesda Category I): Value of Ultrasonography

Abstract

One possible result of fine-needle aspiration (FNA) of thyroid nodules is "nondiagnostic" cytology. Consensus exists in these cases to repeat FNA guided by ultrasonography (US), but the result obtained may continue to be nondiagnostic. The objective of this study was to evaluate predictive factors of malignancy (including US) in nodules with indication for FNA whose cytology result was classified as "nondiagnostic" on 2 occasions. The sample consisted of 158 patients with thyroid nodules >5 mm with indication for FNA whose material obtained by US-guided FNA was classified as nondiagnostic on 2 occasions according to the criteria of the Bethesda classification. Papillary thyroid carcinoma (PTC) was confirmed by histology in 23/158 cases (14.5%). Sex, age, family history of PTC, palpation, number of nodules, serum TSH, or circulating antithyroperoxidase antibodies were not predictors of malignancy. Only US predicted risk of malignancy. US showed a sensitivity of 65.2% and a specificity of 90.4%. When US indicated the nodule to be "suspicious for malignancy", histology confirmed PTC in 15/28 cases (positive predictive value 53.4%). When the nodule showed no suspicious US features, histology detected malignancy in only 8/130 cases (negative predictive value 94%). The diagnostic accuracy of the US was 89.5%. The present results suggest that, in cases of patients with thyroid nodules and repeatedly nondiagnostic cytology, ultrasonographic findings represent an excellent parameter for the selection of those who could be followed up by periodic US and those who should be referred for thyroidectomy because of the risk of malignancy.