BACKGROUND Hashimoto's thyroiditis (HT) and higher levels of thyroid-stimulating hormone (TSH) have been proposed as risk factors for papillary thyroid cancer (PTC), but this issue is still being debated. The purpose of this study was whether HT was related to the risk of PTC over TSH.

METHODS We enrolled 1329 patients (1028 with PTC, 52 with follicular thyroid cancer, and 249 with benign disease) of 1490 patients who underwent thyroidectomy.

RESULTS The TSH concentration was not different among patients with PTC or benign disease. Our study showed that men (odds ratio [OR] = 1.54; p = .049) and the presence of HT (OR = 2.96; p <.001) increased the risk of PTC. Moreover, HT was associated with multifocal cancer (p = .005) and smaller tumor size (p = .031), but it did not influence the extrathyroidal invasion or nodal metastasis.

CONCLUSION Clinicians who deal with thyroid nodules should pay particular attention to HT because it is a stronger predictor for PTC than other risk factors.