Although microdissection of tumor endothelium does not yield a pure endothelial isolate as visualized by detection of mRNA impurities such as pericyte-associated genes NG-2, αSMA, and desmin, judging from the small enrichment of these molecules relative to that of CD31 and VE-cadherin, their contribution to the population of dissected cells is minor. This evidence concerns the gene ACTA1 and neoplasm.