A case of chronic eosinophilic leukemia with secondary transformation to acute myeloid leukemia.

The natural history of primary eosinophilia remains highly variable and is characterized by underlying disease heterogeneity. Chronic eosinophilic leukemia, not otherwise specified (CEL-NOS) is a rare and aggressive disease characterized by non-specific cytogenetic abnormalities or elevated blasts, with high risk of transformation to acute leukemia. We describe a case of CEL-NOS with two hierarchically related non-specific cytogenetic rearrangements, associated with an NPM1 mutation and followed by evolution to secondary AML. NPM1 mutations are not previously described in CEL-NOS.