PTPRC and malignant colon neoplasm: Regardless of the isolation method used, the detection of these cells is confirmed in some cases by (1) visualization of an intact nucleus using a DNA binding fluorescent stain, DAPI (4′,6-diamidino-2-phenylindole); (2) expression of cytokeratin and other epithelial or specific cell surface markers such as SNAIL and ALDH1 (used to isolate CTCs in colon cancer); and/or (3) absence of expression of a white blood cell marker, such as CD45—the leukocyte-common antigen gene [1,17,18,19].