Combined, the frequent methylation in CRC and the very low background of methylated DNA seen in wbc DNA suggests that IRF4, BCAT1 and IKZF1, similarly to SEPT9, are excellent candidate biomarkers, while additional genes such as COL4A2, SOX21, DLX5 and GRASP deserve further consideration. Here, COL4A2 is linked to colorectal carcinoma.