Predictive factors of malignancy in patients with cytologically suspicious for Hurthle cell neoplasm of thyroid nodules

Background: Our aim was to evaluate predictive factors of malignancy in patients with cytologically suspicious for Hurthle cell neoplasm (HCN) of thyroid nodules. Materials and methods: We searched cases with cytologically suspicious for HCN from 11,569 ultrasound-guided fine-needle aspirations (US-FNA) performed at our institution. Nodules that were confirmed surgically or followed-up for at least 2 years were compared with respect to age, gender, tumor size, US diagnosis, and US findings to predict malignancy. Results: The incidence of cases with cytologically suspicious for HCN was 1.2% (143 of 11,569). Of 75 nodules that underwent sufficient follow-up or surgery, malignancies were found in 11 (14.7%). Malignant histological examination revealed oncocytic variants of papillary thyroid carcinoma (PTC) in 3 cases, classic PTC in 1, Hurthle cell carcinoma in 3, follicular carcinoma in 3 and an unclassified carcinoma in 1. In univariate analysis, tumor size was significantly larger in malignant nodules compared to benign nodules (p=0.026). The best cut-off value of tumor size in predicting malignancy was 2.5cm. (p=0.006, sensitivity: 63.6%, specificity: 79.7%). The incidences of hypoechogenicity and malignant US diagnoses were higher in malignant nodules than in benign nodules (p<0.001). In multivariate analysis, tumor size was an independent factor in predicting malignancies. (p=0.037, odd ratio: 2.09, confidence interval: 1.046-4.161). Conclusion: Preoperative US provides predictive factors of malignancy in thyroid nodules with cytologically suspicious for HCN. Predictive factors include tumor size of 2.5cm or greater, hypoechoic nodule and malignant US diagnosis.