Thyroid autoimmunity and risk of malignancy in thyroid nodules submitted to fine-needle aspiration cytology

Background: It is a controversial issue whether the risk of cancer for a thyroid nodule is different in patients with Hashimoto’s thyroiditis (HT) and in patients without thyroid autoimmunity. Some studies have reported an increased risk of malignancy in thyroid nodules associated with HT while only limited data based on fine-needle aspiration cytology (FNAC) are available. Methods: Between May 2005 and April 2011, 3279 ultrasonography-guided FNACs were performed on 2255 patients. In all patients serum FT4, FT3, TSH, CT, anti-thyroglobulin (TgAb) and anti-thyroperoxidase (TPOAb) antibody were determined. Results: Patients with suspicious nodules had lower age (44.00±16.24 vs 55.56±13.33 years; P<0.001) and smaller maximum lesion diameter (13.23±7.2 vs 15.69±7.93 mm; P=0.004). Patients with TgAb positivity had suspicious nodules more frequently than patients without TgAb (8.5 vs 5.1%; P=0.03), independently from TSH levels. No significant difference was recorded between benign and suspicious nodules in gender ratio, in the rate of positive TPOAb or in the rate of both autoantibody positivity. Risk factors for thyroid cancer suspicious cytology were: younger age (OR 0.94; P<0.001), smaller maximum diameter (OR 0.95; P=0.004), single lesion (OR 1.99; P=0.007), microcalcifications (OR 3.80; P<0.001), and TgAb positivity (OR 1.73; P=0.04). Mixed content of the lesion resulted as a protective factor (OR 0.30; P<0.001). All these factors being included into a multivariate logistic regression analysis model, only age, mixed content and microcalcification confirmed significance. By computing FNAC report classes separately, no significant difference results between TPOAb positive or negative groups and between TgAb positive or negative groups. Conclusions: Thyroid nodules in patients with HT are not more frequently cancerous than those in patients without thyroiditis. Positive TgAb is – however - an independent predictor for suspicious cytology in thyroid nodules, independently from TSH levels. Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project. Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.