Asociation beween thyroid autoimmunità and papillary thyroid carcinoma: recent confirmation form a prospective study.

Introduction: The association between autoimmune thyroid diseases and papillary thyroid carcinoma (PTC) is still controversial and it is based only on retrospective analyses. Objective: Aim of the present research was to evaluate this association in a prospective study of unselected consecutive thyroid nodules (TN) submitted to fine-needle aspiration cytology (FNAC), anti-thyroid autoantibodies (ATA) measurement and histological analyses of surgical samples. Subjects and methods: 196 patients (252 nodules) with TN were studied. 106 patients (142 TN) had undetectable ATA (ATA-), while 90 (110 TN) were ATA positive (ATA+), including 78 (93 TN) with definite autoimmune thyroid disease (AITD) with hyper or hypothyroidism and/or extranodular thyroid hypoechogenicity on ultrasound. Cytology was classified as benign (TIR 2), indeterminate (TIR 3), suspect (TIR 4) and malignant (TIR 5). Of 61 patients (75 TN) submitted to total thyroidectomy, histological diagnosis and lymphocytic thyroid infiltration (LTI) description were available for the present report. Results: A significantly higher prevalence of classes TIR 4-5 (20% vs 9.8%, p<0.05) and lower prevalence of class TIR 2 (59.1% vs 63.4%, p<0.05) were found in ATA+ vs ATA- nodules, respectively. These differences were even more evident when only TN with coexistent AITD were compared to ATA- group (TIR 4-5, 22.6% vs 9.8%, p<0.01; TIR 2, 53.8% vs 63.4%, p <0.01). Histological analysis confirmed a significantly increased prevalence of thyroid cancer, mostly PTC, (68.8% vs 44.2%, p <0.05) in AITD vs ATA– group, while a higher prevalence of LTI was also observed in malignant vs benign nodules (66% vs 34%, p <0.05). Conclusions: To our knowledge this is the first prospective study, carried out on a unselected series of consecutive thyroid nodules, confirming the significant association between AITD and PTC, described only in retrospective analyses.