The prognostic role of angiogenesis in breast cancer.

Angiogenesis is of key importance in the process of tumour progression in a number of tumour types including breast cancer. Breast cancer angiogenesis has been the most extensively studied and now serves as a paradigm for understanding the biology of angiogenesis and its effects on tumour outcome and patient prognosis. The first study to examine intra-tumoural microvessel density (IMD) immunohistochemically, and relate it to tumour outcome, was carried out by Weidner and colleagues in 1991 using an antibody against factor-8 related antigen as an endothelial marker in a series of breast cancers. They found a near linear relationship between increased microvessel counts and metastasis. This work defined the standard methodology still used today for the morphometric assessment of IMD, such that by evaluating only three so called "hotspot" areas it was possible to determine the metastatic potential of a tumour. The biological rationale behind this was that these highly angiogenic areas were those most likely to be the easiest point of entry for tumour cells into the systemic circulation. Since this initial work there have been many studies which confirm these findings and have related angiogenesis to poor prognosis using a variety of antibodies including those to CD31 and CD34. Angiogenesis is also potentially a unique target for anti-tumour therapy, and much research is being carried out in this area, including blockade of angiogenic signalling pathways and the therapeutic use of antiangiogenic factors.