[Tumor and angiogenesis]

Angiogenesis is a fundamental event in the process of tumour growth. Tumours recruit precursor cells originated in the bone marrow or stimulate local cells to form new blood vessels. Angiogenesis is not necessary initially for malignant transformation. Tumours acquire later the angiogenic phenotype after a variable period of time for each tumour. The molecular mechanism that promotes angiogenesis requires growth factors activation and loss of function of angiogenic inhibitors, although the full process has been poorly understood. Tumour vessel quantitation has been proposed as a prognostic factor predictive of metastatic dissemination. The microvessel density index usually can be assorted by tumour vessel counts at 200x magnification with the light microscopy. Thus, new therapies that have been reported to inhibit tumour angiogenesis are currently under investigation in clinical trials.