Increased numbers of endothelial progenitor cells in peripheral blood and tumor specimens in non-small cell lung cancer: a methodological challenge and an ongoing debate on the clinical relevance.

Bone marrow-derived endothelial progenitor cells (EPC) play an important role in neovascularisation and tumor growth. However, the clinical relevance of EPCs on blood vessel formation in non-small cell lung cancer (NSCLC) is unclear. EPC numbers in circulation are very low and therefore their detection is technically challenging.