Learning Objectives: Introduction Definition of CML Philadelphia Chromosome Normal Granulopoiesis Pathogenesis of CML Aetiology Incidence Clinical Features Phases of CML Lab Diagnosis of CML Course & Prognosis Differential Diagnosis Brief Overview of Treatment

1. Chronic Myeloid Leukaemia
Dr. Rabiul Haque
Lecturer, Department of Pathology
Holy Family Red Crescent Medical College, Dhaka
Youtube.com/c/RabiulHaque

2. Learning Objectives:
• Introduction
• Definition of CML
• Philadelphia Chromosome
• Normal Granulopoiesis
• Pathogenesis of CML
• Aetiology
• Incidence
• Clinical Features
• Phases of CML
• Lab Diagnosis of CML
• Course & Prognosis
• Differential Diagnosis
• Brief Overview of Treatment

3. Introduction
• Chronic myeloid leukaemia (CML) is a myeloproliferative
neoplasm characterized by predominant proliferation of gr
anulocytic cells.
• It is a clonal neoplastic haematopoietic stem cell disorder.
• The defining characteristic of CML is presence of Philade
lphia chromosome and/ or BCR/ABL fusion gene in all t
he neoplastic cells.

4. Evidence for clonal origin of CML

5. Evidence for clonal origin of CML
• Clonal disorders arise from a single stem cell,
• All the neoplastic cells contain either G6PD A or G6PD B
enzyme.
• In CML erythroid, myeloid, and megakaryocytic elements
all contain a single G6PD enzyme.

6. Definition
• By WHO definition, CML is established by identification
of the clone of haematopoietic stem cell that possesses t
he balanced reciprocal translocation between chromosom
es 9 and 22, forming Philadelphia chromosome .
• Ref. Harsh Mohan Text Book of Pathology, 7th Edition

7. Philadelphia Chromosome (Ph Chromosome)
• Formed by translocation between chromosome 22 and ch
romosome 9.
• BCR (Breakpoint Cluster Region) gene of chromosome 2
2q11 is traslocated to fuse with ABL (Abelson) gene locat
ed on chromosome 9q34.
• The fusion product so formed is termed “Ph chromosome
t(9;22) (q34;11), BCR/ABL” which should be positive for
making the diagnosis of CML.

8. Philadelphia Chromosome (Ph Chromosome)

9. Philadelphia Chromosome (Ph Chromosome)
• The site of breakpoint in BCR gene is variable.
• Therefore the size of BCR/ABL protein varies from 185 k
Da to 230 kDa.
• Most patients with typical CML have 210 kDa fusion prote
in.

10. Philadelphia Chromosome (Ph Chromosome)

11. Pathogenesis of CML
• ABL protein is activated to function as a tyrosine kinase e
nzyme that in turn activates other kinases which inhibits a
poptosis.
• Ability of ABL to act as DNA-binding protein is altered.
• Binding of ABL to actin microfilaments of the cytoskeleton
is increased.

12. Normal Granulopoiesis

13. Aetiology
• There are no familial associations in CML.
• The risk of developing CML is not increased in monozygo
tic twins or in relatives of patients.
• No associations exist with exposures to benzene or other
toxins, fertilizers, insecticides, or viruses.

14. Aetiology
• Exposure to ionizing radiation (e.g., nuclear accidents, ra
diation treatment or ankylosing spondylitis or cervical can
cer) has increased the risk of CML, which peaks at 5–10
years after exposure and is dose-related.

15. Aetiology
The median time to development of CML among atomic bomb survivors of
Hiroshima was 6.3 years.

16. Aetiology
Following the Chernobyl accident, the incidence of CML did
not increase, suggesting that only large doses o radiation can cause CML.

17. Incidence
• CML is primarily a disease of adults but also occurs in chi
ldren and adolescents.
• The peak incidence is in the fifth to sixth decades of life.

18. Clinical Features
• Onset is insidious.
• Mild to moderate anaemia and hypermetabolism leads to
fatigability, weakness, anorexia and weight loss.
• In case of splenomegaly dragging sensation in the abdom
en may be felt.
• In case of splenic infarct acute onset of left upper quadra
nt pain may be present.

19. 3 Phases of Chronic Myeloid Leukaemia
• Chronic Phase
• Accelerated Phase
• Acute Blast Crisis

20. Chronic Phase of CML
• Leukaemic cells retain the capacity for differentiation and
maturation and are largely able to function normally.
• The disease is responsive to chemotherapy and remains
stable for variable period.
• The duration of this stage is 3 to 5 years.

21. Accelerated Phase of CML
• Leukaemic cells show increasing loss of differentiation an
d maturation, increased proliferation, and resistance to ch
emotherapy.
• Chronic phase gradually evolves into accelerated phase i
n 70% of the cases.
• Disease becomes more aggressive.
• Majority of the cases may progress to acute blast crisis p
hase within a span of few months.

22. Acute Blast Crisis Phase of CML
• This occurs when there is transformation to acute leukae
mia and the disease becomes extremely resistant to che
motherapy.
• Median survival is 2 to 6 months.
• About 30% of patients progress to blastic phase without i
ntervening accelerated phase.

23. Lab Diagnosis of CML
• Peripheral Blood Examination
• Bone Marrow Examination
• Cytogenetic Analysis

24. Lab Diagnosis of Chronic Phase of CML
• A. Peripheral Blood Examination:
– Anaemia: Mild to moderate, normocytic and normochromic.
– Total leucocyte count is moderately to markedly raised and is c
ommonly more than 1,00,000/cmm.
– All stages of maturation from myeloblast to segmented neutrop
hils are present with ‘peaks’ of myelocytes and segmented neut
rophils.
– Blast cells are less than 10%.
– Basophilia is important for diagnosis of CML since it is rarely se
en in any other disorder.

25. Lab Diagnosis of Chronic Phase of CML
Stages in the formation of mature neutrophils

26. Lab Diagnosis of Chronic Phase of CML
Normal Mature WBCs

27. Lab Diagnosis of Chronic Phase of CML
Blood film in Philadelphia‐positive CML showing: a promyelocyte, an eosinophil
myelocyte, three basophils and a number of neutrophils and band forms

28. Lab Diagnosis of Chronic Phase of CML
CML in chronic phase: leukocytosis, pathologic left shift and increase of
basophils in the peripheral blood. May–Grünwald–Giemsa, ×500.

29. Lab Diagnosis of Chronic Phase of CML
• B. Bone marrow examination:
– Cellularity: Hypercellular
– Myeloid : Erythroid Ration is 10:1 to 50:1 (normal ratio is 2:1 to
4:1 )
– Myeloblast <10%
– Megakaryocytes are frequently increased in number and are ty
pically smaller in size with hypolobated nuclei.

30. Lab Diagnosis of Chronic Phase of CML
Endosteal zone:
myeloid precursors (myeloblasts,
promyelocytes)
Intermediate zone:
myelocytes, erythroid islands
Central zone:
metamyelocytes, bands,
segmented neutrophils, erythroid
islands, and megakaryocytes
Normal Bone Marrow Organization

31. Lab Diagnosis of Chronic Phase of CML
CML in chronic phase: marked increase of granulopoiesis within bone
marrow, Giemsa, ×250

32. Lab Diagnosis of Chronic Phase of CML
• C. Cytogenetic Analysis:
– Cytogenetic analysis of bone marrow and peripheral blood sho
ws a characteristic abnormality, the Ph’ chromosome in more th
an 95% of the cases.
– In some cases of CML, Ph’ chromosome cannot be demonstra
ted by cytogenetic analysis.
– However, in most such patients rearrangement of BCR/ABL ca
n be demonstrated by Southern blot analysis, fluorescent in sit
u hybridisation or polymerase chain reaction.

33. Lab Diagnosis of Accelerated Phase of CML
• According to WHO classification, accelerated phase is chara
cterized by presence of one or more of the following features:
– Blast cells are 10–19% in the peripheral blood film and bone marro
w.
– Peripheral blood basophilia ≥20%.
– Persistence of thrombocytopaenia (<1 lac/cmm) unrelated to therap
y or persistent thrombocytosis (>10 lac/cmm) not responsive to ther
apy.
– Progressive splenomegaly and increase in leucocyte count.
– Cytogenetic evidence of clonal evolution.

34. Lab Diagnosis of Accelerated Phase of CML
Blasts, promyelocytes, and atypically maturing forms with nuclear atypia;
also several small basophils are seen.

35. Lab Diagnosis of Accelerated Phase of CML
Five ‘pseudo-Pelger’ cells in Accelerated phase of CML indicating there
has already been disease evolution.

36. Pelger–Huët anomaly Shows hypolobated neutrophils. Chromatin in coarsely
clumped and granule content is normal. (Autosomal dominant)

37. Lab Diagnosis of Accelerated Phase of CML
CML in accelerated phase: focal marrow fibrosis (MF) with
micromegakaryocytes (m) and pseudo-Gaucher cells (p). ×125

38. Lab Diagnosis of Blast Crisis Phase of CML
• According to WHO classification, blast crisis phase is cha
racterized by presence of one or more of the following fea
tures:
– Blasts in peripheral blood or bone marrow ≥20%.
– Blast proliferation at a site other than bone marrow.
– Focal clustering of blasts in bone marrow.
• Blast crisis in CML may be myeloid (70%) or lymphoid (3
0%).

39. Lab Diagnosis of Blast Crisis Phase of CML
Large number of blasts cluster together with a high white blood cell count.

40. Course & Prognosis of CML
• Chronic phase of CML may run a stable course with a me
dian duration of about 3.5 years.
• Chronic phase gradually evolves into accelerated phase i
n 70% of the cases.
• About 30% of patients progress to blastic phase without i
ntervening accelerated phase.
• Median survival is 2 to 6 months in blast crisis phase.

41. Course & Prognosis of CML
• At diagnosis, prognostic factors associated with shorter d
uration of survival are –
– Older age
– Large spleen and liver size
– Increased number of blasts
– Increased number of basophils
– Fibrosis of bone marrow.

42. Differential Diagnosis of CML
• Non-neoplastic changes, particularly leukemoid reaction
• Other myeloproliferative neoplasms, especially primary m
yelofibrosis and essential thrombocythemia
• Myelodysplastic/myeloproliferative neoplasms, particularl
y atypical CML and CMML
• Myelodysplastic syndrome with del(5q) chromosome aber
ration 5. De novo acute leukemia.

43. Differences between chronic myeloid leukaemia and leukaemoid reaction
Traits CML Leukaemoid Reaction
Clinical Features Splenomegaly According to underlying
cause
PBF WBC count Usually >1,00,000/cmm Usually <50,000/cmm
Myelocyte and
neutrophil ‘peaks’
Present Absent
‘Toxic’ granules Absent Present
Basophilia, eosinophilia,
monocytosis
Present Absent
Bone marrow
examination
Trilineage hyperplasia Myeloid hyperplasia
Genetic analysis Ph’ chromosome or
BCR/ABL gene
rearrangement
Normal

44. Traits CML Polycythaemi
a vera
Essential
thrombocythaemi
a
Primary
myelofibrosis
Blood
smears
All stages of
myeloid
maturation,
‘peaks’ of
myelocytes and
segmented
neutrophils.
Thick smear
due to
erythrocytosis
Thrombocytosis
with marked
variation in size
Leuco-
erythroblastic
reaction
Bone
Marrow
Trilineage
hyperplasia with
granulocytic
predominance
Trilineage
hyperplasia
with erythroid
predominance
Numerous
dispersed, large,
mature
hyperlobated
megakaryocytes
Predominant
granulocytic
hyperplasia;
highly bizarre
megakaryocyte
s in tight
clusters
Predominan
t cell line
affected
Granulocytic Erythroid Megakaryocytic Granulocytic
and
megakaryocytic
Mutation BCR-ABL fusion JAK2V617F
(>95%)
JAK2V617F
(50%); MPL
JAK2V617F
(50%); MPL

45. Chronic myelomonocytic leukaemia (CMML):
• Usually presents with anaemia and splenomegaly in elder
ly persons.
• There is moderate leucocytosis, neutrophils and band for
ms are increased, and monocyte count is in excess of 10
00/cmm.
• Bone marrow typically shows trilineage dysplasia and incr
ease in monocytic cells.
• Basophilia, Ph’ chromosome, or BCR/ABL gene rearrang
ement are absent.

46. Treatment of CML
• The treatment of CML was revolutionized in 1998 when i
matinib mesylate, a potent and specific inhibitor of tyrosin
e kinase became available. (First line drug)
• 80% of patients with CML present in chronic phase.
• Majority of patients achieve a complete haematologic res
ponse at 3 months and complete cytogenetic response at
6, 12, or 24 months.

47. Treatment of CML
• Complete haematologic response means:
– Disappearance of all signs and symptoms of CML
– Disappearance of palpable splenomegaly
– Normalization of total leucocyte count and platelet count
– No immature cells (myelocytes, promyelocytes, blasts) on differ
ential count.

48. Treatment of CML
• Complete cytogenetic response means:
– No Philadelphia chromosome positive metaphases

49. Treatment of CML
• For patients showing suboptimal response, options includ
e imatinib dose escalation or alternate tyrosine kinase inh
ibitors like dasatinib or nilotinib.
• For accelerated phase, dasatinib or nilotinib are recomme
nded.
• For blast phase, tyrosine kinase inhibitor therapy either al
one or in combination with chemotherapy followed by allo
geneic haematopoietic transplantation is recommended.

50. Closing Remarks

51. Reference:
• Robbins & Cotran Pathologic Basis of Disease 9th Edition
• Harsh Mohan Text Book of Pathology 7th Edition
• de Gruchy’s Clinical Haematology in Medical Practice 6th
Adapted Edition
• Hoffbrand’s Essential Haematology 7th Edition
• Essentials of Haematology (Shirish M Kawthalkar) 2nd E
dition
• Blood Cells : A Practical Guide 5th Edition