The Wnt pathway, epithelial-stromal interactions, and malignant progression in phyllodes tumours

In a previous study of phyllodes tumours, it has been shown that both the stroma and the epithelium can exhibit distinct molecular changes, suggesting that both are part of the neoplastic process. In view of this finding, it was decided to study stromal-epithelial interactions in these tumours by examining the Wnt-APC-beta-catenin pathway. beta-catenin and cyclin D1 immunohistochemistry was performed on 119 phyllodes tumours. Eighty-six (72%) showed stromal nuclear beta-catenin localization and in 57%, the staining was moderate or strong; however, of the eight malignant tumours in the series, seven showed absent or weak nuclear staining (p < 0.025). In no tumour was nuclear beta-catenin staining seen in the epithelial component. Moderate or strong stromal cyclin D I staining correlated with nuclear stromal beta-catenin staining (p