Recent Updates in Classification of

Myeloid Neoplasms

Guide: Dr. Presented by: Dr. Chirag Parmar

Introduction:•WHO published 3rd and 4th edition of WHO classification of

myeloid and lymphoid neoplasm in 2001 and 2008 respectively as a part of ‘WHO Blue Book’ series.

• In 2014, a clinical advisory committee (CAC) composed of ~100 pathologists, haematologists, oncologists and geneticists from around the world convened to propose revisions to the fourth edition of the WHO classification.

Revision of the 2008 classification is influenced by several factors including following:

• Recently identified molecular features-> new perspective regarding diagnostic and prognostic markers.• Improved characterization and standardization of morphological

features-> aiding in the differentiation in disease groups.• Various clinico-pathological studies and their experiences ->

validates WHO postulate of an integrated approach.

• For these reasons, the fourth edition is being updated, but this 2016 classification is not a major overhaul of the disease categories. • Rather, it is intended to incorporate new knowledge of these

disorders obtained since the 2008 publication and is a revision of that classification.• The purpose of this seminar is to summarize the major changes

in the revised WHO classification of myeloid neoplasms and acute leukemia and to provide the rationale for those changes.

WHO Classification-2016 Myeloid neoplasms(summary)• AML- 25 subtypes; 3 new genetic entities

• MPN- 8 subtypes (new molecular genetic criteria)

• MDS- 7 subtypes (all new names; some integration of molecular)

• MDS/MPN- 5 subtypes; 1 new entity (RARS-T new entity) (new molecular genetic criteria)

WHO classification of myeloid neoplasms and acute leukemiaMyeloproliferative neoplasms (MPN)• Chronic myeloid leukemia (CML), BCR-ABL1• Chronic neutrophilic leukemia (CNL)• Polycythemia vera (PV)• Primary myelofibrosis (PMF)

• prefibrotic/early stage• overt fibrotic stage

• Essential thrombocythemia (ET)• Chronic eosinophilic leukemia, not otherwise specified (NOS)• MPN, unclassifiable

•Mastocytosis

WHO classification of myeloid neoplasms and acute leukemiaMyelodysplastic syndromes (MDS)• MDS with single lineage dysplasia• MDS with ring sideroblasts (MDS-RS)

• MDS-RS and single lineage dysplasia• MDS-RS and multilineage dysplasia

• MDS with multilineage dysplasia• MDS with excess blasts• MDS with isolated del(5q)• MDS, unclassifiable• Provisional entity: Refractory cytopenia of childhood

Myeloid neoplasms with germ line predisposition

WHO classification of myeloid neoplasms and acute leukemiaMyeloid/lymphoid neoplasms with eosinophilia and rearrangement of

PDGFRA, PDGFRB, or FGFR1, or with PCM1-JAK2• Myeloid/lymphoid neoplasms with PDGFRA rearrangement• Myeloid/lymphoid neoplasms with PDGFRB rearrangement• Myeloid/lymphoid neoplasms with FGFR1 rearrangement• Provisional entity: Myeloid/lymphoid neoplasms with PCM1-JAK2

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN)• Chronic myelomonocytic leukemia (CMML)• Atypical chronic myeloid leukemia (aCML), BCR-ABL1 -ve• Juvenile myelomonocytic leukemia (JMML)• MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T)• MDS/MPN, unclassifiable

WHO classification of myeloid neoplasms and acute leukemiaAcute myeloid leukemia (AML) and related neoplasmsAML with recurrent genetic abnormalities

• AML with t(8;21)(q22;q22.1);RUNX1-RUNX1T1• AML with inv(16)(p13.1q22) or t(16;16)(p13.1;q22);CBFB-MYH11• APL with PML-RARA• AML with t(9;11)(p21.3;q23.3);MLLT3-KMT2A• AML with t(6;9)(p23;q34.1);DEK-NUP214• AML with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM• AML (megakaryoblastic) with t(1;22)(p13.3;q13.3);RBM15-MKL1• Provisional entity: AML with BCR-ABL1• AML with mutated NPM1• AML with biallelic mutations of CEBPA• Provisional entity: AML with mutated RUNX1

AML with myelodysplasia-related changesTherapy-related myeloid neoplasms

WHO classification of myeloid neoplasms and acute leukemiaAML, NOS

• AML with minimal differentiation• AML without maturation• AML with maturation• Acute myelomonocytic leukemia• Acute monoblastic/monocytic leukemia• Pure erythroid leukemia• Acute megakaryoblastic leukemia• Acute basophilic leukemia• Acute panmyelosis with myelofibrosis

Myeloid sarcomaMyeloid proliferations related to Down syndrome

• Transient abnormal myelopoiesis (TAM)• Myeloid leukemia associated with Down syndrome

Myeloproliferative neoplasms (MPN)

Myeloproliferative neoplasms (MPN)• Chronic myeloid leukemia (CML), BCR-ABL1+• Chronic neutrophilic leukemia (CNL)• Polycythemia vera (PV)• Primary myelofibrosis (PMF)

• PMF, prefibrotic/early stage• PMF, overt fibrotic stage

• Essential thrombocythemia (ET)• Chronic eosinophilic leukemia, not otherwise specified (NOS)• MPN, unclassifiable

•Mastocytosis

Mastocytosis• No longer considered a subgroup of the MPNs due to its unique

clinical and pathologic features, ranging from indolent cutaneous disease to aggressive systemic disease.•Mastocytosis is now a separate disease category in classification.• Also there is shortening of the name of the 2008 category of

“systemic mastocytosis with associated clonal hematological non-mast-cell lineage disease (SH-AHNMD)” to the 2016 category of “systemic mastocytosis with an associated hematological neoplasm (SM-AHN).”

Chronic Myeloid Leukemia•Most of the CML chronic phase cases can be diagnosed from

PS along with BCR ABL 1 positivity t(9,22).• Although the accelerated phase in uncommon in TKI era,

there is no universal accepted criteria for diagnosis of AP.• The criteria for AP in revised classification includes clinical,

haematological, morphological and cytogenetic parameters along with evidence of resistance to TKI therapy.• ‘Response to TKI therapy’ criteria are still provisional until

further supported by additional data.

Chronic Myeloid Leukemia

Chronic Neutrophilic Leukemia• In recent years, data have emerged that suggest the need

for revisions to the diagnostic criteria for the BCR-ABL1-ve MPNs.• The CSF3R mutation is strongly associated with chronic

neutrophilic leukemia (CNL).

Polycythemia vera• Polycythemia Vera (PV) is possibly underdiagnosed using

the hemoglobin levels published in the fourth edition, and the utility of BM morphology as a reproducible criterion for the diagnosis of PV is recognized.• So required haemoglobin levels as a criteria are reduced

and incorporated with PV bone marrow morphology to prevent underdiagnoses of PV.

Polycythemia vera

ET vs. prePMF• The discovery of novel molecular findings in addition to JAK2 and

MPL mutations, in particular the CALR mutation, provide proof of clonality, diagnostic importance, and influence prognosis.• It is necessary to differentiate “true” essential thrombocythemia

(ET) from prefibrotic/early primary myelofibrosis (prePMF). Among other features, the morphologic findings in the BM biopsy, including the lack of reticulin fibrosis at onset, and this distinction has prognostic implications.• The minor clinical criteria in prePMF that may have a major impact

not only on accurate diagnosis but also on prognosis need to be explicitly defined.

Summary of the Changes for MPN

• Inclusion of novel molecular findings in addition to JAK2 and MPL mutations; in particular the CALR mutation provide proof of clonality, diagnostic and prognosis importance.

• The CSF3R mutation is strongly association with chronic neutrophilic leukemia

• Polycythemia vera (PV) was under diagnosed using the Hgb levels published in the 4th ‐edition, and of the utility of BM morphology as a reproducible criterion for the diagnosis of PV is recognized.

• It is necessary to better differentiate ‘true’ essential thrombocythemia (ET) from prefibrotic/early primary myelofibrosis (pre PMF). ‐• The minor clinical criteria in pre PMF more explicitly defined. ‐• Standardized morphologic criteria of MPNs are important to enhance inter observer ‐reproducibility of morphologic diagnoses (which currently has consensus rates ranging between 76% and 88%, depending on the study design).

Myeloid neoplasms associated witheosinophilia and rearrangement of PDGFRA,PDGFRB, FGFR1 or with PCM1-JAK2

• Criteria for diagnosis of eosinophilia related proliferations are retained.• New entity-> PCM1-JAK2: t(8;9)(p22;p24.1)• It is a rare entity which presents with eosinophilia with BM

finding of left sided erythroid predominance, lymphoid aggregates and often myelofibrosis.

Myeloid neoplasms associated witheosinophilia and rearrangement of PDGFRA,PDGFRB, FGFR1 or with PCM1-JAK2

• Other Tk rearrangements can also present as B-cell ALL. • Also known as BCR-ABL1 like ALL with t(9;12)(p24;p13) ETV6/JAK2.• New provisional category for B-cell leukemia/lymphoma.• Responds to JAK2 inhibition/ TKI.

Myeloid neoplasms associated witheosinophilia and rearrangement of PDGFRA,PDGFRB, FGFR1 or with PCM1-JAK2

MDS/MPN• To include myeloid

neoplasms with features that overlap between MDS and MPN.• Based on accumulated

scientific evidences, a provisional entity RARS-T, now termed MDS/MPN with ring sideroblast and thrombocytosis.

CMML

• A diagnosis of CMML requires both the presence of persistent PB >1 x 109 and monocytes accounting from 10% of WBC.• In addition, blast percentage has prognostic importance.

Recent studies has shown that a more precise prognostication can be obtained.

• Three subgroups of CMML according to blast percentage.

Category PB blast % BM blast %

CMML-0 <2% <5%

CMML-1 2-4% 5-9%

CMML-2 5-19% 10-19% or/and Aur rods+

New data: mutations of SRSF2, TET2, and ASXL1• One of the three above mutations can be identified in at least 90% of CMML cases; other mutations seen less frequently are SETBP1, RAS, RUNX1, CBL, and EZH2. They can be helpful diagnostic adjuncts in difficult cases, particularly given the frequently normal karyotype of CMML.• Co mutation of ‐ TET2 and SRSF2 is seen in about one third of CMML ‐cases and is a specific predictor of the diagnosis. • ASXL1 is a predictor of aggressive disease behavior and has been incorporated into a prognostic scoring system alongside karyotype and clinicopathologic parameters.• NPM1 mutation is seen in a rare subset of CMML (3 5%) and appears to ‐herald a worst prognosis.

Atypical CML

• Rare, <2% of CML t(9;22)/BCR/ABL1 pos.• Patients are older than in CML• Variable splenomegaly• Anemia and variable thrombocytopenia• Neutrophilic leukocytosis (WBC >13x109/L) with Prominent dysplasia of granulocytes (may show abnormal chromatin clumping)• No or minimal basophilia (<2% of WBC)• No or minimal monocytosis (<10% of WBC)

Atypical CML

Atypical CML vs. CNL

• Many times aCML and neutrophilic leukemia is confused with each other as both neutrophilic granulopoesis.• Atypical CML now has better characterization and can be

differentiated more easily from CNL.• CNL is associated with CSF3R mutation which is rare in atypical

CML.• Also so called driver mutations of MPN(JAk2,CALR,MPL) are

typically absent in aCML.

MDS/MPN with ring sideroblasts and thrombocytosis

• RARS-T criteria includes refractory anemia, ring siderobasts(>15%), thrombocytosis(>450K).• Frequently associated with SF3B1 which is associated with

ring sideroblasts.• JAK2 V617F, CALR, MPL may be seen.

MDS/MPN with ring sideroblasts and thrombocytosis

Juvenile myelomonocytic leukemia (JMML)• Juvenile myelomonocytic leukemia (JMML) is an aggressive clonal

hematopoietic disorder of infancy and early childhood characterized by an excessive proliferation of cells of monocytic and granulocytic lineages that is included as a MDS/MPN subtype.• Approximately 90%of patients carry either somatic or germline

mutations of PTPN11, KRAS, NRAS, CBL, or NF1. • The clinical and pathological findings of JMML are not substantially

changed from the current WHO fourth edition (2008). However, molecular diagnostic parameters have been refined.

Myelodysplastic Syndrome• Clonal BM neoplasm with ineffective haematopoiesis

manifested by morphologic dysplasia in hematopoietic cells and peripheral cytopenias.• Cytopenia is ‘must’ for any MDS diagnosis. • Prior classification MDS nomenclature included reference to

cytopenias or to specific cytopenia(eg. Refractory anemia).• However WHO classification relies on degree of dysplasia

and blast percentage, not on the specific cytopenia.

Myelodysplastic Syndrome•Moreover lineage showing significant dysplasia does not

correlate with specific cytopenias.• For these reasons, term refractory anemia is replaced by

MDS followed by single vs multiple dysplasia or RS, EB, 5q del.• No changes in childhood MDS.

Myelodysplastic syndrome

Myelodysplastic Syndrome• Now blasts % are counted using all nucleated cells instead of

non erythroid cells.• So most of the cases of AML M6a(erythroid/myeloid type) fall

into MDS with excess blast.• Those with >20% non erythroid blasts with >50% erythroid

precursor should be categorized based on the typing of the non erythroid blast.• AML M6a(erythroid/myeloid type) is now removed in new

classification.

Acute Myeloid LeukemiaAML with recurrent genetic abnormalities:• The WHO continues to define specific AML by focusing on

significant cytogenetic and molecular subgroup.• In order to stress the significance of PML RARA fusion from

other complex rearrangements other than t(15;17), it is renamed as APL with PML-RARA.• Provisional category AML with BCR-ABL1 is added to recognize

these rare de novo AML cases to benefit from TKI therapy.

Acute Myeloid LeukemiaAML with recurrent genetic abnormalities:• The finding that the improved prognosis associated with AML

with mutated CEBPA is associated with biallelic, but not single, mutations of the gene has resulted in a change in that disease definition to require biallelic mutations.• A provisional category of AML with mutated RUNX1 has been

added to the classification for cases of de novo AML with this mutation which has possibly worse prognosis than other AML types.

Acute Myeloid Leukemia

Acute Myeloid LeukemiaAML with MDS related changes:

• Retained and refined.• NPM1 and CEBPA –ve cases with dysplasia in >50% of cells

of at least two lineages.• Prior cytotoxic therapy and history of MDS must be excluded.

Acute Myeloid LeukemiaAML not otherwise specified

• Only one change is made in AML NOS.• AML M6 -> subcategory erythroid/myeloid type is removed.• AML M6- Pure erythroid leukemia(>80% erythroid precursers

and >30% proeythroblasts).

Myeloid sarcoma•Myeloid sarcoma remains in the classification as a unique clinical

presentation of any subtype of AML.•Myeloid sarcoma may present de novo, may accompany PB and

marrow involvement, may present as relapse of AML, or may present as progression of a prior MDS, MPN, or MDS/MPN. • Although listed separately in the classification, cases of myeloid

sarcoma without evidence of marrow disease should be investigated comprehensively so that they can be classified into a more specific AML subtype.

Myeloid proliferations of Down syndrome• The myeloid proliferations of Down syndrome include • transient abnormal myelopoiesis (TAM) and • Myeloid leukemia associated with Down syndrome.

• Both are usually megakaryoblastic proliferations, with TAM occurring at birth or within days of birth and resolving in 1 to 2 months and myeloid leukemia occurring later, but usually in the first 3 years of life with or without prior TAM and persisting if not treated.

Myeloid proliferations of Down syndrome

• They have a similar behavior that is independent of blast cell count and these are not subclassified into MDS or AML.

• Both TAM and myeloid leukemia associated with Down syndrome are characterized by GATA1 mutations and mutations of the JAK-STAT pathway, with additional mutations identified in the myeloid leukemia cases.

References• Daniel A. Arber, Attilio Orazi, Robert Hasserjian, et el. The

2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia, Blood:2016;127(20):2391-2402.• Attilio Orazi, Updating the WHO Classification of

Myeloproliferative and Myelodysplastic/ Myeloproliferative Neoplasms,ISLH 2016 Milan , Italy. May 12 14‐• Tejinder Singh’s Atlas and Text of Hematology•Wintrobes Clinical Hematology, 13E (2013)