Galectin-3 Immunohistochemical Expression in Thyroid Neoplasms

Background: Galectin-3 has been implicated in the regulation of cellular growth, differentiation and malignant transformation in various organs including thyroid gland. It has been extensively studied as an immunohistochemical (IHC) marker in thyroid malignancy. Aim: To evaluate the diagnostic role of Galectin-3 (Gal-3) in differentiating malignant from benign thyroid neoplasm. Materials and Methods: In this observational study we evaluated Gal-3 expression in a spectrum of malignant (30) and benign (20) thyroid neoplasms. The final common diagnosis arrived at after histopathologic evaluation of H&E stained sections by two pathologist's was considered the gold standard. The malignant neoplasms included Papillary Thyroid Carcinoma (PTC), Follicular Thyroid Carcinoma (FTC), Medullary Thyroid Carcinoma (MTC), insular carcinoma, Anaplastic Thyroid Carcinoma (ATC), and metastatic carcinoma. The benign neoplasms included Follicular Adenoma (FA), Hurthle cell adenoma and hyalinizing trabecular adenoma. IHC staining for Gal-3 was performed for all neoplasms with the polymeric method using lyophilized mouse monoclonal antibody. Statistical Analysis: Statistical analysis was done using 2x2 contingency table. Chi-square test with Yates correction was used to calculate p-value to ascertain statistical significance. Results: Gal-3 expression was significantly higher in malignant thyroid neoplasms as compared to benign neoplasms (p<0.0001). Gal-3 expression in differentiating malignant from benign neoplasms was found to have sensitivity of 86%, specificity of 85%, positive predictive value of 89.66% and negative predictive value of 80.95%. However, no statistical significance was observed (p=0.4718) when comparing PTC and other malignant lesions in terms of Gal-3 expression. Gal-3 expression in PTC was found to have sensitivity of 91.3%, specificity of 85%, positive predictive value of 87.5% and negative predictive value of 89.47%. Conclusion: Diffuse and strong IHC staining for Gal-3 differentiates malignant from benign tumours. This marker can assist in the diagnosis of thyroid neoplasms with equivocal morphologic features. This study highlights the high sensitivity of Gal-3 for PTC.