Hashimoto’s thyroiditis (HT) and thyroid cancer: further serological cytological and histological studies.

OBJECTIVE: We recently showed (Boi F. et al EJE 2005, 153: 637-642) an association between anti-thyroid autoantibodies (ATA) and suspicious thyroid cytology. To further study the association between HT and thyroid tumors, we studied a wider group of consecutive patients unselectively evaluated for thyroid nodules (TN). PATIENTS AND METHODS: A total of 2053 TN was submitted to cytological examination and 301 underwent thyroidectomy. In all series cytology was compared to ATA and in operated patients the presence of diffuse lymphocytic thyroid infiltration (LTI) was assessed by histology. Cytology was classified as benign (class II), indeterminate (class III) and suspicious or malignant (class IV). RESULTS: As shown in the Table, increased prevalence of both III and IV cytological classes and malignant tumors were found in ATA+ TN. Higher prevalence of LTI was also observed in malignant vs benign operated TN. Both ATA and LTI were associated only to papillary thyroid carcinomas (PTC). Class III cytology was more prevalent in ATA+ TN, but the fraction of operated class III TN resulting in malignancy was strikingly lower in ATA+ (1/20, 5%) when compared to ATA- (34/67, 50.7%; p=0.0003). CYTOLOGY (n=2053) CLASS II (n=1472) CLASS III (n=392) CLASS IV (n=189) Group ATA- (n=1400) 1065 (76%) 239 (17%) 96 (6.8%) Group ATA+ (n=653) 407 (62.3%)** 153 (23.4%)** 93 (14.2%)** ** p<0.0001 vs ATA– HISTOLOGY BENIGN MALIGNANT p ATA+ (n=100) ATA– (n=201) n= 34 (34%) n=95 (47.3%) n= 66 (66%) n=106 (52.7%) p<0.05 Malignant vs Benign LTI+ (n=97) LTI- (n=93) n= 18 (38.3%) n=29 (61.7%) n= 79 (55.2%) n=64 (44.8%) CONCLUSIONS: This study provides further evidence supporting an association between HT and PTC. However, the low prevalence of malignancy in ATA+ nodules with indeterminate cytology suggests the presence in HT of follicular cell atypias difficult to discriminate from neoplastic atypias only on cytological grounds.