CD34 and acute myeloid leukemia: This retrospective cohort study aimed to (a) validate ERG immunohistochemistry staining in bone marrow trephine samples in our center, (b) quantify ERG IHC positivity in an AML cohort and correlate concordance with CD34 and CD117 immunostaining, when available, and (c) to see whether ERG is a useful adjunct in the diagnosis of cases of AML where the blast cell population has proven difficult to identify by other means.