Galectin-3 as a presurgical immunocytodiagnostic marker of minimally invasive follicular thyroid carcinoma

Thyroid nodules are a common occurrence in the general population, but only a small number of them are eventually diagnosed as cancers. Fine-needle as piration biopsy (FNAB) is the most accurate and cost-effective method for t he presurgical management of thyroid nodules, but it misses the differentia l diagnosis between thyroid follicular adenomas and follicular carcinomas. Among them, minimally invasive follicular carcinoma (MIC), also defined as encapsulated tumor, only differs from follicular adenoma for the exhibition of minimal, but entire thickness, infiltration of the capsule and/or vascu lar invasion. This feature cannot be assessed in FNAB and can occasionally be hard to recognize in surgical specimens. As reported in several studies, galectin-3 is a reliable marker of thyroid malignancy, but no data are ava ilable on MICs. We analyzed the immunohistochemical expression of galectin- 3 in 17 MICs and 52 follicular adenomas in both preoperative paraffin-embed ded cytological human thyroid sediments (cell blocks) obtained by FNAB and in the corresponding surgical specimens. Among the MICs, all surgical sampl es showed galectin-3 immunoreactivity in the cytoplasm, whereas 16 of 17 co rresponding FNAB cell blocks were positive. No evidence of cytoplasmic gale ctin-3 expression was observed in 48 of 52 adenomas in both cell blocks and histological tissues. These findings indicate that galectin-3 is a reliabl e presurgical molecular marker of MIC, improving the accuracy of convention al FNAB. It also proves to be useful in the histopathological assessment of resected tumors having suspected malignant features.