EOSINOPHILIA
Supervisor: 王建得 主任, 施銘洋 醫生
Presenter: 吳昱徵 醫師,楊曜綸 醫師, 謝博彥 醫師, 吳珮瑜 醫師

Introduction&
Background
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Introduction lymphoid organs /
mucosa of the GI tract

Introduction- impotence of eosinophil
• produce + store more than 30 cytokines, chemokines, and growth factors
→ vital to immune system response
• dysregulation can result in abnormal organ infiltration of the skin, heart,
and lung which can have life‐threatening consequences.

Background
• bone marrow: 1%‐6%
• peripheral blood: 3%‐5% (0.35‐0.5 × 109/L)
• Eosinophilia
mild
• up to
1.5 × 109/L
moderate
• 1.5‐5 × 109/L
severe
• >5 × 109/L

Background
eosinohilia
idiopathic hypereosinophilia (IHE)
idiopathic
hypereosinophilic
syndrome (IHES)
For>6 monthes No cause
be found
organ Involvement
and dysfunction

Diagnosis-histomorphology
• round to oval
• 10 to 15 μm in diameter
• nuclear: cytoplasmic ratio of 1:3
• refractile, coarse, orange‐red granules, uniform in size and
evenly fill the cytoplasm
• mature eosinophil: 80% two‐lobed nucleus with lobes of equal size and
ovoid shape

Eosinophil with atypical
nuclear segmentation
and cytoplasmic
vacuoles
Atypical eosinophil with
cytoplasmic vacuoles
Atypical eosinophil with
uneven granule
distribution and
cytoplasmic vacuoles
Circulating eosinophilic
myelocyte
Hypercellular marrow
with eosinophil
hyperplasia
Normal eosinophil

Diagnosis- Flow cytometric analysis
• Neutrophils[ moderate to bright CD45 + CD33 /CD13(+) ]
• CD11b/CD11c(+)
• CD14/CD16/CD56/CD64/HLA‐DR/CD34/CD117/CD38(-)
• Evaluation of lymphocytic‐variant hypereosinophilia (L‐HES)

Diagnosis- Immunohistochemistry
• Usage: blast enumeration + additional phenotyping
• Ex. CD117 (c‐KIT): exclude the presence of mast cells aggregates
(difficult to identify on hematoxylin and eosin stain alone)
 Exclude systemic mastocytosis

Diagnosis- Immunohistochemistry
• Usage: blast enumeration + additional phenotyping
• Ex. CD117 (c‐KIT): exclude the presence of mast cells aggregates
(difficult to identify on hematoxylin and eosin stain alone)
 Exclude systemic mastocytosis

Diagnosis

Case scenarios&
Etiology
13

Case 1
• A 73-year-old man with history of prostate cancer
• Chief complaint: peripheral eosinophilia (AEC: 1700) for 3
months
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 No constitutional symptoms
 No allergic disorders
 No recent travel
 No skin rashes
 No lymphadenopathy

Ancillary test
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Laboratory panel • Exclude allergic, infectious and autoimmune disorders
Peripheral blood
smear
• No circulating blasts, atypical lymphoid cells, or dysplastic
change
Bone marrow • 11.3% eosinophils with background maturing trilineage
hematopoiesis
Flow cytometry • No atypical immunophenotype
Karyotyping • A normal male karyotype
FISH • Negative for MDS
• No abnormality of PDGFRA

Reactive eosinophilia
• Eosinophilia is secondary in most cases.
• If not, evaluation for a primary eosinophilic disorder should be
performed.
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Case 2
• A 58-year-old man without past medical history
• Chief complaint: fever and skin rash
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 Pruritic skin rash for 4 years, involving
bilateral extremities
 Wax and wane
 No recent travel
 Bilateral axillary lymphadenopathy
 Scaly rash

Ancillary test
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Peripheral blood
smear
• Leukocytosis with eosinophilia (AEC: 4800)
• No circulating blasts, atypical lymphoid cells, or dysplastic
change
Bone marrow • Increased eosinophils with background maturing
trilineage hematopoiesis
Flow cytometry • A small CD3 and CD4 positiveT-cell population with
aberrant loss of CD7
Karyotyping • A normal male karyotype
FISH • Negative for MDS
• No abnormality of PDGFRA

Biopsy
• Skin
Fibrosis of papillary dermis
Psoriasiform changes
Hyperkeratosis with mild perivascular chronic inflammation with no
epidermotropism
• Lymph node
Dermatopathic lymphadenitis
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Lymphocytic-variant hypereosinophilic
syndrome (L-HES)
• A clonal expansion of phenotypically aberrantT-cells with a
subsequent secondary eosinophilia
• Often present with cutaneous manifestations
• End-organ damage including cardiac and neurologic
involvement
• Development of overtT-cell neoplasms is well described.
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Case 3
• A 74-year-old woman with history of allergic rhinitis and
transient ischemic attack
• Chief complaint: flu-like symptoms for 3 months
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 Fever, weakness, fatigue, night sweats, and
early satiety
 No recent travel
 Splenomegaly without lymphadenopathy

Ancillary
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Cardiac workup • Restrictive cardiomegaly and mitral valve regurgitation
Peripheral blood
smear
• Leukoerythroblastic smear
• Neutrophilia, including a left shift to few blasts (7%)
• Eosinophilia (AEC: 16400) with atypical and immature
forms
Bone marrow • Hypercellular marrow
Flow cytometry • Myeloid predominant marrow with increased basophils
Karyotyping • A gain of chromosome 8 without t(9;22)
FISH • No abnormality of PDGFRA/PDGFRB/FGFR1

Chronic eosinophilic leukemia, not
otherwise specified (CEL, NOS)
• Myeloproliferative neoplasm: a clonal population of eosinophil
precursors, with blast < 20%
• Molecular genetic abnormality:TET2, ASXL1, DNMT3A
Can be seen in a minority of normal elderly people
• Must exclude other MPN and AML
No rearrangement of PDGFRA, PDGFRB, or FGFR1
No PCM1-JAK2 fusion
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Idiopathic hypereosinophilic syndrome
(IHES)
• No increase in blasts
• End organ damage is present.
• Next-generation sequencing positive: similar clinical features
and bone marrow findings as CEL, NOS
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Case 4
48‐year‐old man with a past history of diabetes and hypertension
Syncope, melena, and hematochezia for the past 2 months
Recent unintentional weight loss
No recent travel
Lab: eosinophilia and a leukocytosis
PE and CT: splenomegaly without
lymphadenopathy

Ancillary test
項目
Peripheral smear
• Myelophthisic smear
• Anemia, thrombocytopenia, and atypical eosinophilia
• Hypogranular forms
Bone marrow biopsy
• Hypercellular marrow with marked eosinophilia
• Megakaryocytic atypia including pyknotic forms and atypical
nuclear to cytoplasmic ratios
• No increase in blasts
• Diffuse marrow fibrosis
Flow cytometry No increase in blasts or other aberrancies
Karyotyping Normal male karyotype
FISH
• MDS and t(9;22) was negative
• CHIC2 deletion
• negative for abnormalities of PDGFRB and FGFR1

CHIC2 deletion and PDGFRA‐FIP1L1 fusion

Myeloid and lymphoid neoplasms with eosinophilia
• Aberrant tyrosine kinase activity due to fusion abnormalities
 Platelet‐derived growth factor receptor α (PDGFRA) <similar to CEL, NOS>
 Platelet‐derived growth factor receptor β (PDGFRB) <similar to CMML>
 Fibroblast growth factor receptor 1 (FGFR1)
 PCM1-JAK2 fusion gene
• Uncontrolled eosinophil proliferation
• Mast cells may be increased
 Differentiate from Systemic mastocytosis

Myeloid and lymphoid neoplasms with eosinophilia
Tyrosine kinase activity

Myeloid and lymphoid neoplasms with eosinophilia
• Bone marrow evaluation:
 Hypercellular marrow with granulocyte hyperplasia and eosinophilia
 Often with accompanying fibrosis
• Karyotyping can identify abnormalities of PDGFRB, FGFR1, and
PCM1‐JAK2
• 4q12 deletion (CHIC2) is usually seen with abnormalities of PDGFRA
 Requiring FISH
• Treatment with imatinib results in an excellent response

Other Neoplasms associated with eosinophilia

Chronic myeloid leukemia, BCR‐ABL1‐positive
• Myeloproliferative neoplasms
 Major proliferative component with granulocytes
 Philadelphia chromosome
• Peripheral absolute basophilia and eosinophilia with left shift
• Marrow: Small megakaryocytes with hypolobated nuclei
 Megakaryocyte hyperplasia or myeloid hyperplasia
Identify the chromosomal translocation

Dwarf megakaryocytes
Micromegakaryocytes, or dwarf
megakaryocytes
increased nuclear to cytoplasmic ratios and
hypolobated nuclei

Systemic mastocytosis
• Major criteria
 Multifocal, dense infiltrates of mast cells (≥15 mast cells in aggregates)
detected in sections of bone marrow and/or other extracutaneous organs
• Minor criteria
 In biopsy or bone marrow aspirate smears, >25% of the mast cells in the
infiltrate are spindle‐shaped or have atypical morphology
 Detection of an activating point mutation at codon 816 of KIT in mast cell
Mast cells in bone marrow, blood or other extracutaneous organ express CD25
with/without CD2 in addition to normal mast cell markers
 Serum total tryptase persistently exceeds 20 ng/mL (unless there is an
associated myeloid neoplasm, in which case this parameter is not valid)

Systemic mastocytosis
• SM and neoplasms associated with eosinophilia can present with
similar clinicopathologic features
• Via detection of dense aggregates of mast cells with IHC
 CD117 and/or mast cell tryptase, CD25, CD2
• The mast cells in SM are almost always CD25 positive and CD2
positive in two thirds of cases

Acute myeloid leukemia
• inv(16)(p13.1q22) or t(16;16) (p13.1;q22);CBFB‐MYH11
 may also present with eosinophilia
• Unlike most cases of AML
 Blast count of 20% is not required to render this diagnosis
• Increased blasts with monocytic differentiation
• Necessitating FISH analysis for diagnosis
 CBFB‐MYH11
• Harlequin cell

Harlequin cell
Eosinophils which may manifest with large,
prominent, dark, basophilic granules, and
atypical nuclei

Classic Hodgkin lymphoma
• B‐cell neoplasm composed of mononuclear Hodgkin cells and classic
Reed‐Sternberg cells
• Typically associated with lymphadenopathy
• Not infrequently presents with reactive, non‐clonal peripheral
eosinophilia
 Utilizing IHC to diagnose CHL
• Hodgkin cells have a unique morphology and immunophenotype,
typically expressing CD30, CD15, and PAX5 (reduced)

Chronic myelomonocytic leukemia
• Features of both a MPN and a MDS
• Absolute monocytosis
 Can be associated with peripheral eosinophilia as well
• In patients with CMML and prominent eosinophilia, abnormalities of
PDGFRB must be excluded

Approach
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Approach to eosinophilia
• A detail history and review of system
Duration of the eosinophilia as well as associated B‐symptoms including fever, night sweats,
and unintentional weight loss
Travel and medication history
Skin rashes, lymphadenopathy, cardiorespira‐ tory symptoms, and gastrointestinal symptoms
• Physical exam
Rash, lymphadenopathy, and organomegaly
• Lab
Chest radiography, echocardiogram, serum troponins, and oxygen saturation assess
end‐organ damage
CBC/DC, metabolic panel, tryptase, ESR, CRP,Vit B12, IgE levels and/or allergy testing, PB
smear

Approach to eosinophilia
• Review CBC parameters and PB smear
Isolated eosinophilia reactive eosinophilia
Cytopenias, basophilia, circulating blasts, and/ or leukoerythroblastosis genetic and
molecular test
PB smear
• Eosinophil morphology atypia including hypogranulation, atypical segmentation, mature
eosinophils with atypical basophilic granules
• Granulocyte morphology dysplasia such as abnormal nuclear segmentation or
hypogranular cytoplasm
• Red cell morphology anisocytosis and poikilocytosis, including dacrocytes and/or circulating
nucleated red blood cells
• Platelet morphology abnormal changes in platelet number, granularity, and size

Next steps to take
• Bone marrow biopsy detecting hematologic malignancies, metastatic disease,
and potentially infections
• Flow cytometry
Increased blasts (but <20%) CEL
abnormalT‐cell population L‐HES
aberrant expression of CD25 and/or CD2 on mast cells SM, but CD25 positivity can be
seen in mast cells of myeloid/lymphoid neoplasms with eosinophilia and rearrangement
of PDGFRA, PDGFRB, or FGFR1, or with PCM1‐JAK2
• Immunohistochemistry
Mast cell v.s SM CD117 and/or mast cell tryptase
CD30,CD15, and PAX5 Classic Hodgkin lymphoma

Next steps to take
• Cytogenetic testing (including FISH and RT-PCR)
4q12 (PDGFRA), 5q31‐q33 (PDGFRB), 8p11‐12 (FGFR1), or 9p24 (JAK2) myeloid and
lymphoid neoplasms with eosinophilia
PDGFRA abnormalitiesCEL
PDGFRB abnormalities CMML
AML with inv(16)(p13.1q22) or t(16;16)(p13.1;q22);CBFB‐MYH11
• Molecular test (NGS)
TET2,ASXL1, and DNMT3A CEL
ASXL1,TET2, EZH2, and SETBP1 a subset of IHES

Flow cytometryCD3‐CD4+,
CD3+CD4‐CD8‐, and
CD3+CD4+CD7‐

Key problem areas
• Many reactive causes of eosinophilia exist History!!!!
• Cryptic cytogenetic abnormalities including, but not limited to inv(16) and CHIC2
deletions, that cannot be identified through conventional karyotyping require
FISH or RT‐PCR analysis
• Lack of consensus criteria for the diagnosis of L‐HES closely follow up as they
may develop overt lymphoma
• Clonal molecular genetic abnormalities (ie, TET2, ASXL1, and DNMT3A) seen in
CEL, NOS can also be seen in a minority of elderly people in the absence of a
hematologic malignancy

Thank you
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Reference
• Rebecca L. Larsen, Natasha M. Savage. How I investigate Eosinophilia. Int J Lab
Hem. 2019;41:153–161.
• GildaVarricchi, Maria Rosaria Galdiero, et al.. Eosinophils:The unsung heroes in
cancer? Oncoimmunolog. 2018; 7(2): e1393134.
• N. Savage, et al. Myeloid neoplasms associated with eosinophilia and
rearrangement of PDGFRA,PDGFRB, and FGFR1: a review. 2013; 35(2): 491-500
• Teresa Scordino. Morphologic variants of normal cells. 2016
• LeonardNaymagon, et al. Eosinophilia in acute myeloid leukemia: Overlooked and
underexamined. 2019; 36: 23-31
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