CD33 and leukemia: Several normal cell surface antigens, such as CD33 [41, 42], CD123 [43, 44], CD47 [45, 46], CD371 (CLL‐1 or CLEC12A) [47, 48], CD70 [49], CD366 (TIM3) [50, 51], and IL1RAP [52, 53, 54], have been found to be either more highly expressed or to display selective expression on MDS and AML leukemia propagating cells; but it remains unclear to what degree they can reliably identify the entire leukemia stem cell population.