Tessier-Cloutier B, et al. - Researchers studied claudin-4, an epithelial intercellular tight junction protein, expression in undifferentiated endometrial carcinomas (UECs)/dedifferentiated endometrial carcinomas (DDECs) and other high-grade uterine carcinomas in this analysis. Results of this study suggested that claudin-4 expression can be absent or very focal in a subset of high-grade endometrial carcinomas, and was almost always absent in the undifferentiated components of switch/sucrose non-fermentable (SWI/SNF)-deficient UECs/DDECs, notwithstanding the apparent epithelial origin in the case of DDECs, therefore, claudin-4 expression cannot be used to infer mesenchymal or epithelial tumour origin in the endometrium. Data reported that the consistent loss or down-regulation of claudin-4 in SWI/SNF-deficient UECs/DDECs further supported the undifferentiated nature of these tumours.