Expression of galectin-3 in fine-needle aspirates as a diagnostic marker differentiating benign from malignant thyroid neoplasms

BACKGROUND. Galectin-3 is a beta-galactoside-binding protein that has been reported to be expressed preferentially in thyroid malignancies. The curren t study was designed to substantiate this finding further and to establish a presurgical diagnostic modality of differentiating between benign and mal ignant 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 metastat ic anaplastic carcinomas, 3 primary medullary carcinomas, 25 follicular ade nomas, 3 goiters, and 58 adjacent normal thyroid tissue. Alternatively, epi thelial cells were isolated from the fine- needle aspirates of 14 thyroid n odules and subjected to immunoblotting analysis of galectin-3. RESULTS. Immunohistochemical analysis revealed that all thyroid malignancie s of follicular cell origin (including papillary, follicular, and anaplasti c 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 thyr oid adenomas, goiters, nor normal thyroid tissues expressed galectin-3. Imm unoblot analysis of the isolated epithelial cells detected galectin-3 in ni ne thyroid nodules that were proven histologically to be malignant (eight p apillary carcinomas and one follicular carcinoma) after surgical interventi on, 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 follicu lar cell origin. Analysis of galectin-3 expression in fine-needle aspirates enhances the differential diagnostic accuracy between benign and malignant thyroid neoplasms. Cancer 1999;85:2475-84, (C) 1999 American Cancer Societ y.