Fig. 2

The interface between intervillous space and uterine tissue: endometrial arcade. a A thin and cellular layer, indicated by black arrowheads, delineates the boundary between intervillous space and endometrial stroma of the arcade. b The layer between intervillous space and endometrial stroma stains mutually exclusively with cytokeratin (green; indicated by green arrowheads) and vimentin (red; indicated by red arrowheads). c The cytotrophoblastic cell column is continuous with the cytokeratin-positive segment of the layer. d The layer stains discontinuously with CD31. CD31-negative portion of the layer is continuous with the cell columns. e The layer stains discontinuously with vWF. Asterisk shows perivillous fibrin-type fibrinoid. IVS = Intervillous space, cc = cell column of the cytotrophoblast