Galectin-3 (GAL3), encoded by LGALS3, is a member of the galectin family of β-galactoside-binding lectins.  GAL3 is involved in many biological process, such as cell growth and differentiation, cell-cell and cell-matrix adhesion interactions, angiogenesis, and apoptosis.  It is expressed in normal breast epithelial cells, inflammatory and various malignant cells.  Recent investigators have found GAL3 involved in tumor progression and metastasis, and its expression valuable in differentiating between benign and malignant thyroid neoplasms.  Thyroid carcinomas are histologically classified into four subtypes: papillary, follicular, medullary, and anaplastic/undifferentiated.  The papillary and follicular carcinomas are derived from follicular epithelium while the medullary subtype is derived from parafollicular cells (C cells).  Anaplastic carcinoma also originates from follicular epithelium, but are highly aggressive.    GAL3 was expressed in most thyroid malignancies of epithelial origin from fine-needle aspirate and open biopsies.  GAL3 did not stain normal thyroid tissues or benign follicular adenomas.  In a panel of 5 diagnostic markers (GAL3, FN1, CITED1, CK19, and HBME1), GAL3 demonstrated the highest sensitivity and accuracy in the differential diagnosis of benign and malignant tumors with follicular architecture.  Fibronectin 1 (FN1) and GAL3 co-expression was diagnostic of carcinoma; their absence was indicative for benign lesions. GAL3 may be a useful marker for thyroid carcinomas of follicular cell origin (including papillary, follicular, and anaplastic carcinomas).