The GEP pattern of increased expression early HSC markers such as CD34 and decreased expression of mature markers such as CD13, CD38 and CD44 in the relapsed group along with increased expression of other genes in the stem cell pathway (n = 51) suggests that there could potentially be a shift to a more immature phenotype and a potential expansion in the leukemia initiating compartment in the RAPL patients. The gene discussed is CD38; the disease is leukemia.