Figure 1.

Identifying VM and EDV by PAS and CD31 double staining ((a), (b)). (a) The VM channel (black arrow) in human sample is formed by head and neck squamous carcinoma cells. There are red blood cells in the center of the channel. PAS-positive substances line the channel and form a basement membrane-like structure (pink) (magnification: ×400). (b) Endothelium-dependent vessels (black arrows) are lined by spindle-shape endothelial cells, which are stained by CD31 (brown). The vessels' basement membrane is positive for PAS staining (pink) (magnification: ×200).