CRLF2 and precursor B-cell acute lymphoblastic leukemia: In addition, patients with high CRLF2 expression were more frequently positive for the stem cell marker CD34 (85.7% vs. 55.6%, P = 0.010) and the myeloid markers CD13 (60.7% vs. 33.3%, P = 0.029) and CD33 (59.3% vs. 30.6%, P = 0.023), which are indicative of a poor prognosis in B-ALL patients.