Galectin-3 immunostaining in cytological and histopathological diagnosis of thyroid lesions

Galectin-3 is a human lectin linked to malignant transformation in different organs including thyroid gland. We aimed to evaluate the diagnostic role of galectin-3 in differentiating benign from malignant thyroid lesions in cytological and histological samples.

This study included a total of 79 cases; 19 multinodular goiter (MNG), 19 follicular adenoma (FA), 13 follicular carcinoma (FTC) and 28 papillary carcinoma (PTC). Galectin-3 immunostaining was applied on histological sections from all the cases (retrospective analysis) as well as for the available preoperative FNAC (28 cases) (prospective analysis).

Retrospective analysis: The positivity percentage of galectin-3 was 10.5%, 92.3%, 93% for nonmalignant, FTC and PTC respectively. According to H score, glaectin-3 immunostaining was significantly lowered in FA) 1+/-2.8 as compared to papillary (158.5+/-88.6) and follicular carcinoma (150+/-83.9) (p>0.0001). However, there was no statistically significant difference between FTC and PTC (p=0.56) or between classic and follicular variants of PTC (p=0.51). Sensitivity, specificity, positive and negative predictive values for galectin-3 staining were 93%, 89.5%, 90.5% and 92% respectively. Prospective analysis: There were five benign, six malignant and 17 indeterminate cytology cases. Galectin-3 immunostaining was able to detect the benign nature of 11/17 indeterminate cytology. Combination of standard cytological evaluation with galectin-3 immunostaining markedly improved sensitivity (71% versus 85%), specificity (75% versus 94%), positive predictive value (83% versus 92%) negative predictive value (60% versus 87.5%) and diagnostic accuracy (72% versus 90%).

We suggest Galectin-3 as a supplementary immunostaining in histological diagnosis of difficult thyroid follicular lesions and in preoperative evaluation of indeterminate thyroid cytology to avoid unnecessary aggressive surgical interference in benign lesions.