  The transformation of the regular vasculature in normal tissue into a highly
inhomogeneous tumor specific capillary network is described by a theoretical
model incorporating tumor growth, vessel cooption, neo-vascularization, vessel
collapse and cell death. Compartmentalization of the tumor into several regions
differing in vessel density, diameter and in necrosis is observed for a wide
range of parameters in agreement with the vessel morphology found in human
melanoma. In accord with data for human melanoma the model predicts, that
microvascular density (MVD, regarded as an important diagnostic tool in cancer
treatment, does not necessarily determine the tempo of tumor progression.
Instead it is suggested, that the MVD of the original tissue as well as the
metabolic demand of the individual tumor cell plays the major role in the
initial stages of tumor growth.
