High prevalence of suspicious cytology in thyroid nodules associated to thyroid autoimmunity

OBJECTIVE: The association between thyroid autoimmunity and thyroid cancer has been suggested, but is difficult to prove due to selection bias of surgical series. Aim of this study was to retrospectively evaluate unselected thyroid nodules submitted to ultrasound (US)-guided fine needle aspiration cytology (FNAC). SUBJECTS AND METHODS: We reviewed 424 FNAC obtained from unselected consecutive thyroid nodules referred to our outpatient service. Nodules were classified in three classes of increasing risk of malignancy: low risk or benign (class II); mild increased risk (class III) and suspect or clearly malignant (class IV). Cytological results were then analyzed according to the presence (ATA+) or absence (ATA-) of associated serum anti-thyroid antibodies as marker of associated thyroid autoimmunity. Histologic examination was available in 51 patients submitted to thyroidectomy. RESULTS: Cytological distribution was: class II 266 (196 ATA-, 70 ATA+), class III 115 (71 ATA-, 44 ATA+) and class IV 43 (21 ATA-, 22ATA+). Statistical analysis showed higher prevalence of classes III and IV cytologies in ATA+ nodules when compared to ATA- (32.3% vs. 24.6%, 0.1>p>0.05 for class III; 16.2% vs. 7.3%, p<0.01, for class IV). Histological examination of 51 patients with class III and IV nodules submitted to thyroidectmy displayed a similar percentage of thyroid malignancy in ATA + (12/19, 63%) and ATA- nodules (19/32, 59%). CONCLUSIONS: This study shows that unselected thyroid nodules associated with serum ATA display higher frequency of suspicious FNAC. Since the prevalence of thyroid malignancy in classes III-IV nodules was similar in ATA+ and ATA– patients, a higher prevalence of thyroid cancer should be expected in ATA+ thyroid nodules. Further studies including a larger number of histological data are needed to confirm this association.