['The Wnt pathway is important in cell signalling transduction and is involved in the pathogenesis of multiple tumour types. A comprehensive analysis of the expression of Wnt signalling pathway proteins in mammary phyllodes tumours (PTs) has not been previously performed.', 'To evaluate the immunohistochemical expression of Wnt pathway proteins in a cohort of PTs, to determine their role in tumour pathogenesis and to identify any associations with patient outcome.', '65 PTs (34 benign, 23 borderline and 8 malignant) diagnosed at a single institution between 1990 and 2006 were analysed. Immunohistochemical stains were performed on tissue microarrays for beta-catenin, Wnt1, Wnt5a, SFRP4 and E-cadherin. Stroma and epithelium were scored separately.', 'Stromal cytoplasmic Wnt5a and SFRP4 expression showed significant progressive increases in expression with increasing grade (p = 0.002 and p = 0.02 respectively). Epithelial membranous and stromal nuclear beta-catenin, epithelial cytoplasmic Wnt1 and epithelial E-cadherin all also showed increasing expression with increasing tumour grade, however, the differences were not significant. Disease-free survival was significantly decreased (p = 0.0017) with positive epithelial E-cadherin staining.'] Are proteins from the Wnt pathway involved in the pathogenesis and progression of mammary phyllodes tumours?