Hashimoto's Thyroiditis Is Not Associated with Increased Risk of Thyroid Cancer in Patients with Thyroid Nodules: A Single-Center Prospective Study

Background: The risk of thyroid carcinoma in patients with thyroid nodules associated with Hashimoto's thyroiditis (HT) is a debatable issue. The studies defining the true risk of thyroid malignancy are scanty and mainly depend on retrospective series. To eliminate inherent bias of retrospective studies, this prospective study was carried out to evaluate the true malignancy rate of unselected thyroid nodules in patients with HT who underwent fine-needle aspiration cytology (FNAC). Methods: These prospective data were gathered on all patients newly diagnosed with thyroid nodules who were sent for FNAC between May 2006 and August 2009. All patients were evaluated for the presence of HT diagnosis by measuring thyroid autoantibodies. If a patient had at least one positive thyroid autoantibody, then the patient was defined as HT with thyroid nodules. There were 164 patients (147 women and 17 men) with thyroid nodules associated with HT (HT group). There were 551 patients (432 women and 119 men) with thyroid nodules without HT (control group). All patients underwent FNAC and ultrasonography (US). Results: The malignancy rate was 1.0% in HT group (2 out of 191 nodules) and 2.7% in the control group (19 out of 713 nodules), a not significant (p = 0.19) difference. In the two cytologically malignant nodules in HT group and 19 in the control group, papillary thyroid carcinoma was diagnosed after thyroidectomy and histopathological examination. US features of nodule echogenicity, structure, margin, and Doppler flow were similar between the two groups. US features of microcalcification and absence of peripheral halo were more prominent in the nodules of the control group (p = 0.002 and p < 0.001, respectively). Conclusions: On the basis of cytopathological criteria, thyroid nodules in patients with HT are no more likely to be malignant than in those without HT. Many of the US features of benign thyroid nodules are similar in patients with and patients without HT.