Expression of Polypeptide N-Acetylgalactosaminyl Transferase-3 and Its Association with Clinicopathological Factors in Thyroid Carcinomas

Background: Polypeptide N-acetylgalactosaminyl transferase-3 (GalNAc-T3) has been reportedly expressed in several human adenocarcinomas and is associated with clinicopathological features of tumors. We investigated the clinicopathological significance of GalNAc-T3 in thyroid cancer. Methods: We evaluated the expression of GalNAc-T3 in 167 patients with thyroid cancer using a specific antibody and analyzed the association between its expression and clinicopathological features. Results: GalNAc-T3 was expressed in 85.8% of normal follicular epithelial cells. In papillary carcinomas, positive staining was observed in 101 (73.7%) cases. Well-differentiated components (papillary and follicular) of papillary carcinomas were significantly more frequently positive than poorly differentiated components (trabecular and solid) (p<0.01), and GalNAc-T3 was highly expressed in papillary carcinomas that had invaded beyond the thyroid capsule (p=0.026). GalNAc-T3 was expressed in 40% and 20% of well and poorly differentiated components of follicular carcinomas, respectively. Thirteen of 15 anaplastic carcinomas were negative for GalNAc-T3 and thyroglobulin. Positive staining for GalNAc-T3 was not observed in any of the medullary carcinomas. Conclusions: Our data suggest that GalNAc-T3 expression may be a useful indicator of tumor differentiation in thyroid carcinomas.