Evaluation of the Prognostic Value of Solute Carrier Family 34 Member 2 "SLC34A2" in Papillary Thyroid Carcinoma: An Immunohistochemical Study

Background. Papillary thyroid carcinoma (PTC) usually has an indolent clinical course, yet a subset of patients might show an aggressive course. Thus, better stratification of at-risk patients is mandatory for proper management. Solute carrier family 34 member 2 (SLC34A2) is an independent prognostic indicator in several cancers. However, only a few studies have been conducted to evaluate the prognostic value of SLC34A2 in PTC, with none of them assessing its immunohistochemical (IHC) expression in a large cohort of patients with PTC or exploring its possible relationship with tumor progression. Aim of the Study. We aimed to evaluate the IHC expression of SLC34A2 in a large series of PTC patients, correlate its expression with established clinicopathological factors, and find any possible relationship between this marker and patient prognosis. Material and Methods. A total of 476 samples (including 238 samples of PTC and 238 samples of normal thyroid tissue) collected between 2002 and 2005 were extracted from the archives of the Pathology Lab, Ain Shams University Hospitals. IHC analysis was performed using an anti-SLC34A2 antibody. Follow-up data were obtained. Results. High SLC34A2 expression significantly correlated with important adverse clinicopathological parameters of PTC-i.e., late tumor stage, positive extrathyroid extension, tumor size > 4 cm, and age >= 55 years (p <= 0.001 for each). Kaplan-Meier analysis revealed that high SLC34A2 expression significantly correlated with shorter disease-free survival (DFS; p=0.005), but not with overall survival (p=0.111). Multivariate analysis showed SLC34A2 to be an independent prognostic factor affecting DFS. Conclusions. High SLC34A2 IHC expression correlated with adverse clinicopathological prognostic parameters. Furthermore, SLC34A2 was identified as an independent factor for DFS that could serve to improve risk stratification of PTC patients for better management.