These results further imply a correlation between the age of the stroma/microenvironment and the relative increase of the size of the pool of myeloproliferation-initiating stem cells and the frequency of immature myeloid cells in PB and are in line with a previously reported clinical study observing a significantly higher number among elderly AML patients showing immature (CD34+/CD33+) blast cell population [38], [39]. The gene discussed is CD33; the disease is acute myeloid leukemia.