Descriptive analysis and quantification of angiogenesis in human brain tumors.

Quantitative determination of the degree of vascularity has been shown to be independently prognostically significant in many human tumor types. In particular, tumor vascularity has known importance in astrocytomas, in which endothelial proliferation is a criterion for anaplasia in many grading schemes. This review analyzes reports of microvessel quantification performed on histologic sections of human brain tumors, and in which correlations with clinical outcome, or other pathobiologic factors have been made. Among the conclusions are: (1) brain tumors have the unique feature of complex 'glomeruloid' vessels, as well as heterogeneity of microvascular distribution and caliber; (2) lower-grade astrocytomas may incorporate pre-existing vessels, while glioblastomas may develop new vessels; (3) quantification may have additional independent prognostic value over and above routine histologic grade in low-grade astrocytomas with low tumor cell proliferative indices. These findings have implications for the appropriateness of antiangiogenic therapies.