Aim: Despite fine-needle aspiration biopsy (FNAB) is the cornerstone of assessment of thyroid nodules, when cytology suggests a follicular neoplasm (FN) only histology can differentiate between benign and malignant lesions. Aim of this study was to evaluate factors predictive of malignancy in cytologically indeterminate FN.
Methods: All the patients who underwent FNAB between December 2007 and November 2008 were considered. Among them, those with a cytology of FN (Thy3, British Thyroid Association) and with an histological control were included. Age, sex, ultrasound characteristics, nodulÈs size, thyroid disease, HBME-1 and Galectin-3 immunocytochemical stains and histology were registered.
Results: Among 1585 FNAB, 261 (16.5%) had a cytology of FN and 195 had an histological control: 146 benign and 49 differentiated thyroid carcinoma (DTC) (43 follicular variant of papillary carcinoma and 6 follicular carcinoma). The malignancy rate in case of single nodules was significantly higher than in multinodular goiter (30/63 Vs 19/132) (P<0.001). Positive immunostaining for both HBME-1 and Galectin-3 was observed in 58 cases, negative for both in 137. The malignancy rate was significantly higher in HBME-1 and Galectin-3 positive nodules (42/49 Vs 16/146) (P<0.001). The risk of malignancy was 1:4 for the entire series, but it increased to 1:2.1 (47.6%) for single nodules and 1:1.4 (72.4%) for HBME-1/galectin-3 positive nodules.
Conclusions: One in four patients with FN has a DTC. Thyroidectomy is mandatory in all the patients with single and/or HBME-1/galectin-3 positive nodules, because of the increased risk of malignancy, and suitable in all the other cases.
