Differential reactivity for galectin-3 in Hurthle cell adenomas and carcinomas

Hurthle cell carcinomas behave as the most aggressive variant of differentiated thyroid carcinoma of follicular origin, with frequent recurrences and higher morbidity. Its differential diagnosis with Hurthle cell adenoma remains a problem for the clinician and for the pathologist. The vertebrate lectins, galectin-1 and galectin-3 have been implicated in the regulation of cellular growth, differentiation, and malignant transformation in thyroid neoplasms. Galectin-3, a beta-galactoside binding protein, has been recently found to be highly expressed in papillary and follicular carcinomas. The current study was undertaken to investigate immunohistochemical reactivity for galectin-3 of thyroid specimen tissues with Hurthle cell adenomas (n = 14) and carcinomas (n = 17), follicular (n = 14) and papillary (n = 11) carcinomas, colloid goiter (n = 30), Hashimoto's thyroiditis (n = 11), follicular adenoma (n = 9), and normal thyroid tissues (n = 18). Follicular (78.5%) and papillary (82.0%) carcinomas were frequently reactive for galectin-3, more often when some Hurthle cells were present. There was no galectin-3 immunostaining in any of the specimens from Hashimoto's thyroiditis, colloid goiters or normal thyroid samples, whereas only one case of follicular adenoma was found positive (11.1%). By contrast, galectin-3 immunostaining in Hurthle cell carcinomas was significantly higher (59%) than in Hurthle cell adenomas (7.1%, p < 0.05). These results suggest that galectin-3 may potentially serve as a marker in difficult differential diagnosis cases involving Hurthle cell adenomas and Hurthle cell carcinomas.