Eosinophilia is defined as a peripheral blood eosinophil count > 0.5x10⁹/L, with > 1.5x10⁹/L of eosinophil count sometimes referred to as hypereosinophlia. Eosinophilia is a common clinical phenotype associated with various conditions including allergies, infections, medications, autoimmune disorders and malignancies. Although malignancy-related eosinophilia is rare, it is an important clinical sign of these tumors, which require early diagnosis and clinical intervention. Figure 1 summaries the initial workup of patients with eosinophilia. , (2) Myeloid/lymphoid neoplasms with PDGFRB rearrangement
 , (3) Myeloid/lymphoid neoplasms with FGFR1 rearrangement
 , (4) Provisional entity: Myeloid/lymphoid neoplasms with PCM1/JAK2

WHO 2016 defines a group of myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1, or with PCM1 / JAK2 as:

(1) Myeloid/lymphoid neoplasms with PDGFRA rearrangement

This group of patients can be treated with tyrosine kinase inhibitors. While patients with PDGFRA or PDGFRB rearrangement are highly sensitive to Imatinib, PCM1-JAK2 patients had varying responses to JAK2 inhibitor Ruxolitinib, which can induce complete remission, although the duration is often limited. FGFR1 inhibitors have not been very successful in treating tumors with FGFR1 rearrangement. PKC412 was effective in a patient with progressive myeloproliferative disorder with (8;13) (Chen et al., 2004); however, subsequent studies with the FGFR1 inhibitor ponatinib were less successful. Novel FGFR1 inhibitors are currently being tested in clinical trials for solid tumors with FGFR1 activation. Recently a new FGFR family kinase inhibitor INCB054828 induced complete resolution of eosinophilia as well as complete hematologic, cytogenetic and molecular remission in a patient with FGFR1 rearranged MPN (Verstovsek et al., 2018).

The fusion partner genes for PDGFRA, PDGFRB, or FGFR1 have been steadily accumulating and are updated below in Tables.
Table 1: PDGFRA fusion partners, chromosome locations, detection methods and references

Gene name	Rearrangements	Detection methods					References (PMID)
		Karyotype	FISH	RT-PCR		NGS
Bibliography Pubmed ID Last Year Title Authors Citation Sheng  Xiao Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1, or with PCM1-JAK2: Overview 2019 Atlas Genet Cytogenet Oncol Haematol. 2019-07-01 Online version: http://atlasgeneticsoncology.org/haematological/1855/js/lib/js/web-card-_common.js External Links OMIM database Cosmic database Genecards database Mitelman database Generate PDF × Please, confirm that you want to generate a PDF file of this page. This may take some seconds once process has started. Then it will be opened automatically. Wait a moment, we are generating the document... Generate PDF Aditional Info × Loading, wait... Close