Neck ultrasonography (NUS) is one of the most commonly used methods for evaluating thyroid nodules and preoperative higher TSH levels are known to be associated with differentiated thyroid cancers. This study was conducted to assess whether serum TSH levels and neck ultrasonography are of value in predicting malignancy in patients with atypia of undetermined significance/follicular lesions of undetermined significance (AUS).

A total of 62 patients (7 men, 55 women; mean age 48.4±11.9 years) who had indeterminate cytologic results indicating AUS underwent thyroidectomy. Preoperative clinical data including serum TSH and the findings of NUS were analyzed retrospectively between malignant and non-malignant groups.

The final pathologic results of malignancy were reported in 53 of 62 (85.5%) patients with AUS. There was no significant difference in the mean value of preoperative serum TSH between malignant and non-malignant groups (1.5±1.3 vs. 1.9±1.2, P=NS). In NUS, the patients diagnosed with malignancy in histology showed a higher proportion of calcification, taller-than-wide shape, hypoechoic texture and irregular margin (58.5% vs. 22.2%, P=0.044; 34% vs. 0%, P=0.038; 98.1% vs. 44.4%, P<0.01; 47.2% vs. 0%, P=0.008).

Serum TSH was not related to malignancy in thyroid nodules showing AUS. However, ultrasonographic features including calcifications, taller-than-wide shape, hypoechoic pattern and irregular margin could be used to predict malignancy. Ultrasonography should be the first useful methods when making decisions regarding management of thyroid nodules showing indeterminate cytologic results as AUS.