Association of positive thyroid auto antibodies with thyroid carcinoma

The association between thyroid autoimmunity and thyroid cancer was carried out in a series of solitary thyroid nodules submitted to fine-needle aspiration cytology and subsequent histopathology. US guided FNACs were obtained from 295 unselected consecutive patients with single thyroid nodules and positive (98) or negative (197) serum anti-thyroid antibody. Cytological results were classified in three classes of increased risk of malignancy: low risk (class II); indeterminate risk (class III); and suspect or malignant (class IV). A higher prevalence of class III (29.6%, p<0.05) and class IV (17.34%, p<0.05) and lower prevalence of class II (52.06%, p<0.01) were found in ATA+ nodules respectively. By multivariate logistic regression analysis ATA+ conferred a significant risk (odds ratio: 1.97 & 95% confidence interval: 0.97-3.97) for class IV cytology independently for age and sex. In 53 patients where thyroidectomy was carried out, thyroid cancer was found in (86.66%) patients with class IV nodules, in (19.4%) of class III nodules (all ATA-) and in none of 7 class II nodules. Histologically proven thyroid cancer (mostly papillary) was then observed in a higher proportion (13.2%) of ATA+, when compared with ATA- nodules (8.1%, p>0.01), but the significance of this finding is limited by the low number of class II nodules operated on. The presence of ATA+ confers an increased risk of suspicious or malignant cytology in solitary thyroid nodules.