Tumor size and age predict the risk of malignancy in Hürthle cell neoplasm of the thyroid and can therefore guide the extent of initial thyroid surgery

Background: The majority of patients having a diagnosis of Hürthle cell neoplasm (HCN) on fine-needle aspiration (FNA) of a thyroid nodule have a diagnostic thyroid lobectomy to make the final diagnosis. If the nodule is malignant, they require a completion thyroidectomy. The objective of this study was to devise a simple clinical scheme capable of predicting malignancy in patients with cytologic diagnosis of HCN and, therefore, guide the extent of initial thyroid surgery. Methods: A total of 57 patients who underwent thyroid surgery after an FNA diagnosis of HCN were retrospectively studied. The patients were examined for clinical features, preoperative imaging studies, and pathology reports. The risk of malignancy was calculated using a multiple logistic regression model. Results: The overall rate of malignancy in patients with HCN was 46% (26/57). The predictors of malignancy based on multiple logistic regression analysis were tumor size >1.5cm (odds ratio [95% confidence interval]=8.0 [1.9-33.4]) and patient age >45 years (odds ratio [95% confidence interval]=2.3 [0.6-8.6]). In patients with nodules larger than 1.5cm, the predicted probability of malignancy was greater in patients over 45 years than in younger patients (65% for >45 years vs. 44% for ≤45 years). In patients with a nodule 1.5cm or less, the probability of malignancy was relatively low and not significantly different between the two age categories (18% for >45 years vs. 10% for ≤45 years). Conclusions: This study suggests that tumor size and age can be integrated into decision making for patients with an FNA diagnosis of HCN to facilitate patient selection for surgical referral and, particularly, to determine in which patients a thyroidectomy rather than a lobectomy should be the initial surgery.