Objective: ACT have an unpredictable clinical behaviour, and no liable histological or molecular parameters are available to predict outcome. The activation of WNT/β-catenin pathway, involved in tumor growth and progression in adult ACT has been explored only in Brasilian pediatric ACT. The aim of this study is the investigation of the possible prognostic role of β-catenin accumulation and/or CTNNB1 (β-catenin gene) mutations also in Italian pediatric ACT.