Using a trypsin-free dissociation protocol (to maintain epitope integrity), we detected the percentage of CSC marker positive cells (e.g., CD34+CD38− for AML, APL, and CML, CD44+CD24− for breast cancer, CD133+ for glioblastoma and colon cancer, and CD271+ for melanoma) in human primary tumors as well as tumor cell lines by flow cytometric analysis. This evidence concerns the gene CD34 and acute promyelocytic leukemia.