The dysregulated tyrosine kinases, D816VKIT and FIP1L1-PDGFRA, are the prototypic oncogenic lesions resulting in systemic mastocytosis (SM) and chronic eosinophilic leukemia, respectively.
The broad and overlapping clinical manifestations of D816VKIT-associated systemic mastocytosis with eosinophilia and FIP1L1/PDGFRA-associated chronic eosinophilic leukemia (CEL), coupled with the increase in activated eosinophils and mast cells seen in both disorders, have led to confusion in the nomenclature.
We investigated the presence of KIT(M541L) in five males with chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), all negative for Platelet-derived growth factor-alpha (PDGFR) or PDGFRbeta abnormalities, which responded to imatinib therapy.