Association between autoimmune thyroiditis and papillary thyroid carcinoma: new confirmations from a large prospective study.

Boi F;Casula S;Arisci N;Serafini C;Satta C;Columbu C;Pani F;Maurelli I;Cappai A;Atzeni F;Taberlet A;Calò PG;Nicolosi A;Lai ML;Mariotti S.

2017-01-01

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Abstract

OBJECTIVE: The association between autoimmune thyroid diseases (AITD) and papillary thyroid carcinoma (PTC) is still controversial and it is based only on retrospective analyses. Aim of this study was to evaluate this association in a large prospective study of unselected consecutive thyroid nodules (TN) submitted to fine-needle aspiration cytology (FNAC). In all series, serum concentrations of anti-thyroperoxidase, TPOAb and anti-thyroglobulin, TgAb (ATA) and TSH were measured before FNAC; histological analyses were performed in all surgical samples. SUBJECTS AND METHODS: A total of 720 patients with a prevalent TN were studied. According to the presence of ATA positivity associated to ultrasound hypoechogenicity and/or hypothyroidism, patients were subdivided in AITD+ (n=263) and AITD- (n=457) groups. Cytology was classified as benign (TIR 2), indeterminate (TIR 3), suspect and malignant (TIR 4-5). Of 102/720 (14.2%) patients submitted to surgery, histological diagnosis and lymphocytic thyroid infiltration (LTI) description were available. RESULTS: A significantly higher prevalence of classes TIR 4-5 (14.9% vs 7.9%) and lower prevalence of class TIR 2 (49.4% vs 62.6%, p<0.002) were found in AITD+ vs AITD- TN, respectively. TSH values resulted higher in AITD+ TN compared to AITD- TN, with the highest values of TSH levels observed in TIR 4-5 vs TIR 2 classes in AITD+ TN (2.26 μU/ml vs 1.11 μU / ml, p <0.01). Histological analysis confirmed a significantly increased prevalence of PTC in AITD+ (35/46, 76.1%) vs AITD- TN (31/56, 55.4%; p<0.05). As expected, the prevalence of LTI was significantly higher in AITD+ (42/46, 91.3%) compared to AITD- patients (18/59, 30.5%, p<0.0001) and an higher prevalence of LTI was also observed in PTC (44/66, 67%) vs benign TN (16/36, 44%; p <0.05). CONCLUSIONS: This large prospective study provides further evidences of the association between PTC and AITD. The demonstration of elevated TSH levels in malignant TN confirms the key role of this hormone in thyroid cell proliferation related to AITD.