TSH Level and Risk of Malignancy in Patients with Bethesda Category IV Thyroid Nodules

Fine needle aspiration biopsy does not permit to distinguish between benign and malignant follicular thyroid lesions (category IV in the Bethesda Cytopathology System). Some reports have suggested an association between increased serum TSH levels and thyroid cancer, so the aim of this study was to investigate the association between TSH levels and malignancy in patients with follicular thyroid nodules. Therefore, we conducted a retrospective study of all subjects who underwent surgical treatment for Bethesda IV thyroid nodules in a single center (years 2012-2017). A total of 127 patients were analyzed, and malignancy was present in 38.6% of the patients. Using ROC analysis, the best TSH cut-off point to differentiate benign from malignant disease was 2.1 mU/l and the age cut-off with better sensitivity and specificity was 47 years. The proportion of subjects with TSH ≥ 2.1 mU/l was greater among subjects with cancer than in those with benign diseases (65.3 vs 44.9%, P = 0.029). The concurrence of both cut-off points (TSH ≥ 2.1 mU/l and age ≥ 47 years) showed a higher diagnostic accuracy than either of the two variables separately. Therefore, the present study supports an association between serum concentrations of TSH and risk of malignancy among subjects with Bethesda IV thyroid nodules. TSH levels could modify the diagnostic and therapeutic approach of patients with Bethesda IV nodules.