CD34 and acute promyelocytic leukemia: In this work, we defined “APL-like” NPM1m AML cases as having a single immunophenotypic population, exhibiting the “double-negative” (CD34- HLADR-) phenotype; cases with two or more immunophenotypic populations including (only one such case was present), or not, a “double-negative” population, were classified in the category of “non-APL-like” NPM1m AML, as our intention was to include purely “APL-like” NPM1m AML in the so-named cohort.