Pure erythroid leukemia: a reassessment of the entity using the 2008 World Health Organization classification.

Pure erythroid leukemia (PEL) is rare, characterized by a neoplastic proliferation of erythroblasts. Given recent incorporation of molecular genetic findings and clinical features in the revised 2008 World Health Organization classification scheme of acute myeloid leukemia, we questioned if PEL still remains as a distinct subtype of acute myeloid leukemia. In this retrospective study, we identified 18 cases of acute leukemia with morphologic and immunophenotypic features of PEL. Following the current World Health Organization classification algorithm, these cases were classified as: 13 acute myeloid leukemia with myelodysplasia-related changes, 3 therapy-related acute myeloid leukemia, and 1 chronic myelogenous leukemia blast crisis, and one unclassifiable due to insufficient clinical information. All 16 cases with cytogenetic data harbored an extremely complex karyotype and the median overall survival of the 18 patients was 3 months (range, 1-7 months). This survival was significantly shorter than that of patients with acute erythroid leukemia, erythroid/myeloid subtype, or acute myeloid leukemia with myelodysplasia-related changes with erythroid predominance (P<0.001). PEL is characterized as a neoplastic erythroid hyperproliferation with maturation arrest. E-cadherin emerged as the most sensitive and specific marker for immature erythroblasts, and was helpful in distinguishing PEL from other erythroid proliferations. Our study showed that the criteria for acute myeloid leukemia in the 2008 World Health Organization system facilitate reclassification of PEL cases into other acute myeloid leukemia categories, mainly of acute myeloid leukemia with myelodysplasia-related changes. These new assigned categories fail to capture the distinct features of PEL, where the phenotype of PEL correlates with a very complex karyotype and an extremely aggressive clinical course.