CD5 and acute lymphoblastic leukemia: Early T-cell precursor acute lymphoblastic leukemia is defined based on immunophenotyping (CD1a-negative, CD8-negative, weak CD5 expression with less than 75% positive blasts, and expression of one or more of the following myeloid or stem cell markers on at least 25% of lymphoblasts: CD117, CD34, HLA-DR, CD13, CD33, CD11b, and/or CD65).