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F Boi, ML Lai, C Deias, M Piga, A Serra, A Uccheddu, G Faa and S Mariotti

OBJECTIVE: To assess the relevance of (99m)Tc-SestaMIBI (MIBI) scan in the diagnostic evaluation of thyroid nodules with oncocytic cytology. SUBJECTS AND METHODS: Twenty-four patients with a single (or prevalent) 'cold' solid nodule with Hurthle cells (HC) at fine needle aspiration cytology (FNAC) were studied. Cytological diagnosis of oncocytic metaplasia (OM) or HC tumor (HCT) was made when HC on the smear were comprised 10-75%, or >75%. Nodules concentrating MIBI at early and late (2 h after washout) stages were considered MIBI-positive. In all cases histological findings were obtained after total thyroidectomy. RESULTS: FNAC was malignant or suspect for malignancy in 16 cases (six HCT and 10 OM) and not suspect in eight (two HCT and six OM). Histological examination revealed 14 malignant tumors (11 HCT and three OM), and 10 benign thyroid lesions (three HCT and seven OM). Sensitivity of FNAC for malignancy was 92.8% and specificity was 70.0%; HCT were identified by FNAC in only 35.7% and OM in 70.0% of cases. No significant difference in MIBI positivity was found between malignant and benign thyroid nodules. The highest percentage of MIBI positivity was found in HCT (78.5%), but MIBI-positive nodules were also observed in thyroid lesions with HC metaplasia (40.0%). CONCLUSIONS: MIBI scintiscan has no value in differentiating malignant from benign HC thyroid neoplasias. Most HCT are MIBI-positive, but this scan is not sufficiently specific to differentiate true HC neoplasias from other thyroid lesions showing HC at FNAC, although an MIBI-negative scan strongly supports the absence of true HCT.

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F Boi, M L Lai, B Marziani, L Minerba, G Faa and S Mariotti

Objective: We assessed the association between thyroid autoimmunity and thyroid cancer in a retrospective series of unselected thyroid nodules submitted to fine-needle aspiration cytology (FNAC) to avoid the selection bias of surgical series.

Subjects and methods: Ultrasound (US)-guided FNACs were obtained from 590 unselected consecutive patients with single thyroid nodules and positive (ATA + , n = 197) or negative (ATA − , n = 393) serum anti-thyroid antibody (ATA). Cytological results were classified in three classes of increased risk of malignancy: low risk or benign (class II); indeterminate risk (class III); and suspect or malignant (class IV).

Results: A higher prevalence of class III (28.9% vs 21.4%, P < 0.05) and class IV (18.8% vs 9.2%, P < 0.001) and lower prevalence of class II (52.3% vs 69.5%, P < 0.001) were found in ATA + vs ATA − nodules respectively. By multivariate logistic regression analysis ATA + conferred a significant risk (odds ratio (OR): 2.29 (95% confidence interval (CI): 1.39–3.76)) for class IV cytology independently from age and sex. In 106 patients where thyroidectomy was carried out, thyroid cancer was found in 54/61 (88.5%) patients with class IV nodules (with similar positive predictive value for cancer in ATA + (96.4%) and ATA– (81.8%) nodules), in 6/31 (19.3%) of class III nodules (all ATA − ) and in none of 14 class II nodules. Non-specific cytological atypias from hyperplastic nodules in lymphocytic thyroiditis probably accounted for the different prevalence of cancer in class III ATA + and ATA − nodules. Histologically proven thyroid cancer (mostly papillary) was then observed in a higher proportion (27/197 = 13.7%) of ATA + , when compared with ATA − nodules (33/393 = 8.4%, P = 0.044), but the significance of this finding is limited by the low number of class II nodules operated on.

Conclusions: The presence of ATA + confers an increased risk of suspicious or malignant cytology in unselected thyroid nodules. Since ATA + is not responsible for increased false- positive class IV FNAC, our study provides indirect evidence supporting a significant association between thyroid carcinoma and thyroid autoimmunity, although further studies with a different design are needed for a definitive histological proof.