Large needle aspiration biopsy and galectin-3 determination in selected thyroid nodules with indeterminate FNA-cytology

Thyroid fine-needle aspiration biopsy ( FNA)- cytology is widely used for the preoperative characterisation of thyroid nodules but this task is difficult for follicular lesions, which often remain undefined. We propose a strategy for improving the preoperative characterisation of selected follicular thyroid proliferations, which is based on large needle aspiration biopsy ( LNAB) and galectin-3 expression analysis. Eighty-five thyroid specimens were obtained by LNAB ( 20- gauge needles) from thyroid nodules with indeterminate follicular FNA-cytology. Aspirated material was processed as a tissue microbiopsy to obtain cell blocks for both cyto/ histo-morphological evaluation and galectin-3 expression analysis, by using a purified monoclonal antibody to galectin- 3 and a biotinfree immunoperoxidase staining method. Preoperative diagnosis was compared to the final histology. LNAB and cell- block technique allow a preliminary distinction between nodules with a homogeneous microfollicular/ trabecular structure, as frequently observed in tumours, and lesions with mixed normo - micro - macrofollicular architecture, as observed in goitre. Furthermore, LNAB provides optimal substrates for galectin- 3 expression analysis. Among 85 cases tested, 14 galectin- 3- positive cases were discovered preoperatively ( 11 thyroid cancers and three adenomas confirmed at the final histology), whereas galectin- 3- negative cases were 71 ( one carcinoma and 70 benign proliferations at the final histology). Sensitivity, specificity and diagnostic accuracy of this integrated morphologic and phenotypic diagnostic approach were 91.6, 97.2 and 95.3%, respectively. In conclusion, LNAB plus galectin- 3 expression analysis when applied preoperatively to selected thyroid nodules candidate to surgery can potentially reduce unnecessary thyroid resections.