CD34 and juvenile myelomonocytic leukemia: This analysis also revealed an aberrant upregulation of CD90/Thy1 expression within the CD34+CD38− fraction in a subset of JMML cases, that persisted in the CD34+/38+ progenitor fraction (Fig. 2a, b and Supplementary Table S2), and could be tracked down to the monocyte population in some patients (not shown).