AIM:Todiscusstherelationshipbetweensmallubiquitin-relatedmodifier4(SUMO4)expression and papillary thyroid carcinoma (PTC).METHODS:The mRNA and protein levels of SUMO4 in PTC and normal thyroid tissues were determined by the methods of real-time PCR, Western blot and immunohistochemistry .The relationship be-tween SUMO4 expression and clinicopathologic parameters in PTC was evaluated .RESULTS:The results showed that both the mRNA and protein levels of SUMO 4 expression in PTC were obviously higher than those in normal thyroid tissues ( P<0.01).CONCLUSION:The high level of SUMO4 expression in PTC suggests that SUMO4 plays an important role in PTC development and it is probably a molecular mechanism of PTC .