Fig. 9

Different populations of vimentin and NANOG-positive (brown) putative stem cells in ovarian sections of women with serous ovarian cancer (in situ): small VSEL-like stem cells with diameters of about 5 μm among epithelial cells in the ovarian surface epithelium and bigger round stem cells with diameters of 10–15 μm separating from the layer of epithelial cells and changing into mesenchymal phenotype. Small stem cells might trigger the epithelial-mesenchymal transition or even develop into bigger round stem cells, putative CSCs, and in this way promote the invasion of ovarian cancer