Vascularization of experimental tumours

At first sight, experimental tumours in observation chambers seem to contain areas with wide vessels showing a sluggish circulation as well as ischaemic areas. Only by careful analysis on cleared specimens can neovascularization be discerned. This process probably occurs primarily in the perimeter of the tumour. It is quite possible that areas of intense vascularization and ischaemic areas in tumours may both result from differences in intensity between the angiogenic stimulus and local tissue pressure.