Figure 3. Immunohistochemical staining for CXCR4. Immunoreactivity for CXCR4 was observed in vascular endothelial cells (A: original magnification 100×) and stromal cells (B: original magnification 40×). Double immunohistochemistry for CXCR4 (red) and c-kit (blue). Cells co-expressing CXCR4 and c-kit were observed in the vascular endothelium (arrows) and in close association with blood vessels (arrowheads). C: original magnification 100×.