Eosinophilia/Hypereosinophilia in the Setting of Reactive and Idiopathic Causes, Well-Defined Myeloid or Lymphoid Leukemias, or Germline Disorders.


Kelemen K(1), Saft L(2), Craig FE(1), Orazi A(3), Nakashima M(4), Wertheim GB(5), George TI(6), Horny HP(7), King RL(8), Quintanilla-Martinez L(9), Wang SA(10), Rimsza LM(1), Reichard KK(8).
Author information:
(1)Division of Hematopathology, Mayo Clinic, Phoenix, AZ.
(2)Department of Pathology, Karolinska University Hospital and Institute, Stockholm, Sweden.
(3)Department of Pathology, Texas Tech University Health Sciences Center, El Paso.
(4)Department of Laboratory Medicine, Cleveland Clinic, Cleveland, OH.
(5)Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA.
(6)Department of Pathology, University of Utah School of Medicine, Salt Lake City.
(7)Institute of Pathology, University of Munich
(LMU), Munich, Germany.
(8)Division of Hematopathology, Mayo Clinic, Rochester, MN.
(9)Institute of Pathology and Neuropathology, Eberhard Karls University of Tübingen and Comprehensive Cancer Center, Tübingen University Hospital, Tübingen, Germany.
(10)Department of Hematopathology, University of Texas MD Anderson Cancer Center, Houston.


OBJECTIVES: To report the findings of the 2019 Society for Hematopathology/European Association for Haematopathology Workshop within the categories of reactive eosinophilia, hypereosinophilic syndrome (HES), germline disorders with eosinophilia (GDE), and myeloid and lymphoid neoplasms associated with eosinophilia (excluding entities covered by other studies in this series). METHODS: The workshop panel reviewed 109 cases, assigned consensus diagnosis, and created diagnosis-specific sessions. RESULTS: The most frequent diagnosis was reactive eosinophilia (35), followed by acute leukemia (24). Myeloproliferative neoplasms (MPNs) received 17 submissions, including chronic eosinophilic leukemia, not otherwise specified (CEL, NOS). Myelodysplastic syndrome (MDS), MDS/MPN, and therapy-related myeloid neoplasms received 11, while GDE and HES received 12 and 11 submissions, respectively. CONCLUSIONS: Hypereosinophilia and HES are defined by specific clinical and laboratory criteria. Eosinophilia is commonly reactive. An acute leukemic onset with eosinophilia may suggest core-binding factor acute myeloid leukemia, blast phase of chronic myeloid leukemia, BCR-ABL1-positive leukemia, or t(5;14) B-lymphoblastic leukemia. Eosinophilia is rare in MDS but common in MDS/MPN. CEL, NOS is a clinically aggressive MPN with eosinophilia as the dominant feature. Bone marrow morphology and cytogenetic and/or molecular clonality may distinguish CEL from HES. Molecular testing helps to better subclassify myeloid neoplasms with eosinophilia and to identify patients for targeted treatments.