Background: Galectin-3 is a beta-galactoside-binding protein that has been reported to be expressed preferentially in thyroid malignancies. The current study was designed to substantiate this finding further and to establish a presurgical diagnostic modality of differentiating between benign and malignant thyroid neoplasms by analyzing galectin-3 expression in fine-needle aspirates.
Methods: The expression of galectin-3 was examined immunohistochemically in total of 172 specimens: 45 primary and 20 metastatic papillary carcinomas, 8 primary and 2 metastatic follicular carcinomas, 5 primary and 3 metastatic anaplastic carcinomas, 3 primary medullary carcinomas, 25 follicular adenomas, 3 goiters, and 58 adjacent normal thyroid tissue. Alternatively, epithelial cells were isolated from the fine- needle aspirates of 14 thyroid nodules and subjected to immunoblotting analysis of galectin-3.
Results: Immunohistochemical analysis revealed that all thyroid malignancies of follicular cell origin (including papillary, follicular, and anaplastic carcinomas) showed high and diffuse expression of galectin-3, whereas one of the three medullary carcinomas of parafollicular cell origin displayed weaker and focal expression of galectin-3. In contrast, neither benign thyroid adenomas, goiters, nor normal thyroid tissues expressed galectin-3. Immunoblot analysis of the isolated epithelial cells detected galectin-3 in nine thyroid nodules that were proven histologically to be malignant ( eight papillary carcinomas and one follicular carcinoma) after surgical intervention, whereas galectin-3 was not detected in five nodules proven to be benign follicular adenomas.
Conclusions: Galectin-3 serves as a marker of thyroid malignancy of follicular cell origin. Analysis of galectin-3 expression in fine-needle aspirates enhances the differential diagnostic accuracy between benign and malignant thyroid neoplasms.