CD34 and colorectal cancer: Microscopically, tumors contained hyperchromatic, pleomorphic cells that stained for monoclonal carcinoembryonic antigen (CEA), polyclonal CEA, cytokeratin 20, vascular markers (CD31, CD34), and vascular endothelial growth factor (VEGF) by immunohistochemistry, supporting involvement by the poorly differentiated HT-29 colorectal cancer cell line.