Objective: CTNNB1 mutations have been found in 15-30 % of Wilms tumour (WT) cases. Nuclear beta-catenin protein has been detected by immunohistochemistry in a higher proportion of WTs, thus suggesting alternative genetic pathways leading to beta-catenin activation in these neoplasms. Method: Sixteen renal WTs and 7 secondary WT localizations were retrospectively investigated. The series included 17 paediatric patients, 10 females and 7 males, with a mean age of 4.5 years and a 34 year-old female patient. Immunohistochemical analysis of beta-catenin was performed and findings were reported for each neoplastic component (i.e. epithelium, stroma and blastema). Tumour DNA was extracted for direct sequencing analysis. Results: The majority of WTs showed moderate to strong membranous staining for beta-catenin in the epithelial (76.5 %) and the blastemal (60 %) components. Nuclear betacatenin expression was observed in combination with cytoplasmic staining in the mesenchyma and/or the blastema of two primary renal tumours. In these cases the deletion of codon 45 p.S45del and the missense substitution p.T41A were detected. Conclusion: Preliminary results of this ongoing study highlight beta-catenin cytoplasmic and membranous expression in the tumour cells of primary and metastatic WTs, with few cases demonstrating nuclear expression. In our series, betacatenin nuclear expression was invariably associated to CTNNB1 mutation.