CD4 and acute myeloid leukemia: In cases with a monocytic/myelomonocytic component (5%–10% of AML cases, but more often seen in high-risk MPN/MDS), CD64, CD11b, and CD4 may be added, such as in the previously proposed special “monocytic tube,” consisting of CD64/CD11b/CD14/CD4/CD34/HLA-DR/CD33/CD45.5,33 This tube relies mostly on lack of CD14 expression on CD4+HLA-DR+CD64+ monocytic cells or lack of HLA-DR, CD4, and CD64 on CD14 positive cells.