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

BACKGROUND Galectin‐3 is a β‐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. Cancer 1999;85:2475–84. © 1999 American Cancer Society. Thyroid carcinomas of follicular cell origin consistently express galectin‐3, whereas neither benign thyroid adenomas nor normal thyroid tissues show detectable amounts of galectin‐3. Immunoblotting analysis of galectin‐3 in fine‐needle aspirates assists in making a presurgical differential diagnosis between benign and malignant thyroid neoplasms.