Galectin-3 cytotest in thyroid follicular neoplasia: a prospective, monoinstitutional study

To analyze the utility of galectin-3 (Gal3) immunohistochemistry (IHC) on preoperatively obtained fine needle aspiration biopsy (FNAB) in identifying the subgroup of follicular neoplasia (FN) patients who were candidates for thyroidectomy.

This prospective, monoinstitutional study applied a standardized Gal3 immunostaining protocol (cell block specimens; Gal3 scores: G0 [no Gal3+ve IHC reaction], G1 [Gal3+ve thyrocytes < or = 10%], G2 [Gal3+ve thyrocytes > 10%) in 100 consecutive cytologically assessed FN. All patients underwent thyroidectomy, and the FNs were always histologically categorized (World Health Organization criteria).

The overall malignancy rate was 15%. Gal3 expression in presurgical samples significantly correlated with the postoperative diagnosis (p < 0.0001). When all positive Gal3 cases were pooled together (G1+G2), the IHC test performed as follows: sensitivity = 80%; specificity = 86%; positive predictive value = 50%; negative predictive value = 96%. All the Gal3-G2 cases (presurgical cell block) showed postoperative evidence of malignancy. All 9 cases of papillary tumor expressed Gal3 in both cell block and postoperative histology. Among the 6 follicular cancers, the prevalence of Gal3 overexpression in the cell block was 50%.

The cell block procedure applied to thyroid FNAB samples enables the Gal3 cytotest to be implemented usefully in the preoperative identification of those cases of FN postoperatively found to be malignant (also significantly reducing the number of inappropriate thyroidectomies). Strong Gal3 expression should prompt immediate surgical treatment.