FCGR1A and acute promyelocytic leukemia: However, the expression of the markers CD4 and CD64 differed between the two entities: some APL cases expressed CD64 (not expressed in “APL-like” NPM1m AML, as this could categorize the case as monocytic/monoblastic NPM1m AML), while the “APL-like” NPM1m AML group showed a tendency for higher CD4 expression compared to APL.