Different microcirculation patterns in melanoma tissue of murine xenograft model. A. Tumor volume in the control group was larger than in the treatment group, suggesting thalidomide inhibits tumor growth. B. VM channel (red arrow) was formed by tumor cells and there were red cells in the center of the channels. PAS-positive substances lined these channels and formed basement membrane-like structure. Yellow arrow indicated EVs presenting in the same field with VM. Endothelial cells were stained as brown by immunohistochemical staining for CD 34, CD34 and PAS double-Staining, 1000×. C. Red arrow showed a VM channel that was lined by brown melanoma cells as well as pink PAS-positive substances. Melanoma cells were identified by HMB45 antibody. HMB45 and PAS double-Staining, 400×. D. In the control group, mitosis was present and VM channels were more numerous under low-magnify field. H&E, 200×.