[Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1].

The 2008 World Health Organization (WHO) classification of tumors of hematopoietic and lymphoid tissues introduced a new category for myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1. Many of these cases present as a myeloproliferative neoplasm, usually with eosinophilia. However, neoplasms associated with rearrangement of PDGFRA can present as acute myeloid leukemia or as T lymphoblastic lymphoma with eosinophilia. Neoplasms associated with rearrangement of FGFR1 even more frequently present as acute myeloid leukemia or T lymphoblastic lymphoma, in both instances with eosinophilia, and both T lymphoblastic and B lymphoblastic transformation of chronic eosinophilic leukemia have also been described. Because of the prominent lymphoid component these disorders have been assigned, in the WHO classification, to a specific category rather than being categorized as a myeloproliferative neoplasm. However, it should be noted that BCRABL1-positive chronic myelogenous leukemia is accepted as a bona fide myeloproliferative neoplasm and yet it too can undergo lymphoblastic transformation and even present as acute lymphoblastic leukemia with the underlying chronic myelogenous leukemia being revealed only after remission has been achieved.