AML , ALL , CML , CLL DIFFERENT AND DIFFERENTIAL DIAGNOSIS.

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Leukemias: AML, ALL, CML, CLL - Comparison and Differential Diagnosis

Origin of Lymphoid vs. Myeloid Neoplasms

Origin of lymphoid neoplasms - B-cell and T-cell differentiation stages

Fig. 13.5 - Stages of B- and T-cell differentiation and the neoplasms arising from each stage (Robbins Pathologic Basis of Disease)

Overview Table: Four Leukemias at a Glance

Feature	AML	ALL	CML	CLL
Cell of origin	Myeloid progenitor	Lymphoid precursor (B or T)	Myeloid stem cell	Mature B lymphocyte
Course	Acute	Acute	Chronic (3 phases)	Chronic (indolent)
Peak age	>60 years	Children (peak 3 yrs)	45-55 years	>60 years
Sex	M=F	M slightly > F	M slightly > F	M:F = 2:1
Key genetic marker	t(15;17), t(8;21), inv(16), NPM1, FLT3	BCR::ABL1 (Ph+), hyperdiploidy, NOTCH1	t(9;22) Philadelphia chromosome (BCR::ABL1)	del 13q14, trisomy 12, del 11q, del 17p
WBC count	Variable (elevated or low)	Variable (elevated, normal, or low)	Markedly elevated (50,000-200,000/µL)	Markedly elevated (small lymphocytes)
Blast count (BM)	≥20% myeloblasts	≥20% lymphoblasts	<10% (chronic); >20% (blast crisis)	Rare blasts; mature lymphocytes
Auer rods	Present (pathognomonic)	Absent	Absent	Absent
Splenomegaly	Mild/absent	Mild	Massive	Moderate
Lymphadenopathy	Mild	Common	Mild	Diffuse (prominent)
Key treatment	Cytarabine + anthracycline; ATRA for APL	Multiagent chemo; TKI for Ph+	Imatinib (TKI)	Ibrutinib, FCR, venetoclax
Prognosis	Variable; poor in elderly	95% remission in children; worse in adults	Excellent with TKI; depends on phase	Indolent; incurable but long survival

1. Acute Myeloid Leukemia (AML)

Definition & Epidemiology

AML is a tumor of hematopoietic progenitors caused by acquired oncogenic mutations that impede differentiation, leading to accumulation of immature myeloid blasts in the marrow. It is the most common acute leukemia in adults, with median age of 60 years (incidence rises to 10/100,000/year in those >60). About 13,000 new US cases/year.

Robbins, Cotran & Kumar Pathologic Basis of Disease

Clinical Features

Onset resembles acute infection: fever, ulcerations of mucous membranes (mouth/throat), fatigue, pallor
Granulocytic insufficiency: infections, mouth ulcers
Anemia and thrombocytopenia (marrow failure)
Lymphadenopathy, splenomegaly, and hepatomegaly are NOT pronounced (distinguishes from CML/ALL)
Untreated: rapidly progressive

Risk Factors

Prior exposure to benzene, ionizing radiation, cytotoxic chemotherapy
Congenital syndromes: Down syndrome, Fanconi anemia, neurofibromatosis, Noonan syndrome

Morphology & Diagnosis

AML myeloblasts with flow cytometry showing CD34/CD64 and CD33/CD15 expression

(A) Myeloblasts with delicate nuclear chromatin, prominent nucleoli, and fine azurophilic granules. (B-C) Flow cytometry showing CD34+/CD64- and CD33+/CD15- myeloid blast phenotype.

Diagnosis: ≥20% blasts in bone marrow or blood
Auer rods (eosinophilic needle-like cytoplasmic inclusions from MPO-positive granules): pathognomonic for AML, absent in ALL
Myeloblasts: 2-4 nucleoli, voluminous cytoplasm, peroxidase-positive granules
Cytochemistry: MPO+, Sudan Black B+, chloroacetate esterase+

Key Genetic Subtypes (WHO Classification)

Genetic Abnormality	Prognosis	Notes
t(8;21); RUNX1::RUNX1T1	Favorable	Core binding factor AML; Auer rods easily found
inv(16); CBFB::MYH11	Favorable	Myelocytic + monocytic differentiation
t(15;17); PML::RARA	Very favorable	APL - responds to ATRA; numerous Auer rods; high DIC risk
KMT2A (11q23) rearrangement	Poor	Monocytic differentiation; gingival hypertrophy
Mutated NPM1	Favorable	Most common single mutation in AML
Myelodysplasia-related genetics	Poor	del 5q/7q; SF3B1, SRSF2 mutations
TP53 mutations	Very poor	Complex karyotype, resistance to standard therapy

Immunophenotype

CD13+, CD33+, CD117+, MPO+, CD34+ (variable); CD3-, CD19-, CD20- (negative for lymphoid markers)

2. Acute Lymphoblastic Leukemia (ALL)

Definition & Epidemiology

ALL is composed of immature B (pre-B) or T (pre-T) cells (lymphoblasts). It is the most common cancer of childhood (~2,500 new cases/year in the US). About 85% are B-ALL; T-ALL tends to present in adolescent males as thymic lymphomas.

Peak incidence: 2-3 years of age for B-ALL; adolescence for T-ALL
Slightly more frequent in boys; highest incidence in Hispanic/Latino children
Robbins, Cotran & Kumar Pathologic Basis of Disease

Clinical Features

Intermittent fevers, bone pain, pallor
Cutaneous/mucosal bleeding, petechiae, purpura
Lymphadenopathy and hepatosplenomegaly: prominent (unlike AML)
Testicular enlargement, subcutaneous nodules (leukemia cutis)
Mediastinal widening on CXR (T-ALL - anterior mediastinal mass)
WBC: elevated, normal, or low; + neutropenia, anemia, thrombocytopenia

Molecular Pathogenesis

T-ALL: NOTCH1 mutations (essential for T-cell development)
B-ALL: mutations in PAX5, TCF3, ETV6, RUNX1, BCR::ABL1, KMT2A, PBX1
Chromosomal: ~90% have numerical/structural changes
- Hyperdiploidy (>50 chr): B-ALL, better prognosis
- Hypodiploidy: B-ALL, worse prognosis
- t(9;22) BCR::ABL1 (Philadelphia chromosome): 25% of adult ALL, poor prognosis - requires TKI
- t(12;21) ETV6::RUNX1: most common translocation in childhood B-ALL, excellent prognosis

Morphology & Diagnosis

Lymphoblasts: scant cytoplasm, finer chromatin, less cytoplasm than myeloblasts
No Auer rods
Diagnosis: ≥20% lymphoblasts in BM

Immunophenotype

B-ALL: CD19+, CD10+ (CALLA), CD22+, TdT+, CD34+, MPO-
T-ALL: CD3+, CD7+, TdT+, CD34+, MPO-
Both: MPO negative (key distinction from AML)

Prognosis

Children: 95% remission rate; ~80% disease-free at 5 years
Adults: significantly worse outcomes
Ph+ ALL requires TKI (imatinib/dasatinib) added to chemotherapy

3. Chronic Myeloid Leukemia (CML)

Definition & Epidemiology

CML is defined by the Philadelphia chromosome - a reciprocal translocation t(9;22)(q34;q11) producing the BCR::ABL1 fusion gene. This generates a constitutively active tyrosine kinase (p210 fusion protein) that drives uncontrolled myeloid proliferation.

CML Histology (peripheral blood and bone marrow):

CML peripheral blood smear showing leukocytosis with myeloid progenitors, basophilia, and bone marrow biopsy showing hypercellularity

(a,b) Peripheral blood: leukocytosis with full range of myeloid progenitors, myelocyte bulge, basophilia, thrombocytosis. (c,d) Marrow aspirate: "dwarf" megakaryocytes, myeloid precursors. (e,f) Marrow biopsy: hypercellularity, thickened paratrabecular cuff - Quick Compendium of Clinical Pathology

Three Phases of CML

Chronic Phase

Leukocytosis (50,000-200,000/µL): neutrophils in all stages of maturation
Myelocyte "bulge" (proportion of myelocytes exceeds other immature forms)
Basophilia + eosinophilia + thrombocytosis (pathognomonic combination)
Low LAP (leukocyte alkaline phosphatase) score - key distinguishing finding from leukemoid reaction
Blasts: usually <1%
Absolute monocytosis in most cases
Massive splenomegaly

Accelerated Phase

One or more of:

Progressive basophilia (>20%)
Thrombocytopenia (<100 × 10⁹/L) unrelated to therapy
Leukocytosis unresponsive to therapy
Clonal cytogenetic progression (extra Ph chromosome, +8, i17q, +19)
Blasts 10-19%

Blast Phase (Blast Crisis)

>20% blasts in blood or marrow - becomes acute leukemia
70% are AML type, 30% are ALL type
Additional cytogenetic abnormalities
Poorly responsive to treatment

Key Lab Findings

Test	CML	Leukemoid Reaction
LAP score	Low	High
Philadelphia chromosome	Positive	Negative
BCR::ABL1 by PCR	Positive	Negative
Basophilia	Present	Absent

Treatment

Imatinib (Gleevec) - competitive inhibitor of ATP binding site of BCR::ABL; also active against PDGFR and c-KIT
2nd line: nilotinib, dasatinib
Resistance mechanism: T315I mutation in BCR::ABL kinase domain; MDR1 overexpression; BCR::ABL amplification
Prognostic monitoring: quantitative RT-PCR for BCR::ABL1 transcript (MRD)

4. Chronic Lymphocytic Leukemia (CLL)

Definition & Epidemiology

CLL is a clonal proliferation of small mature B lymphocytes involving bone marrow, blood, and lymph nodes. It is the most common chronic lymphoid leukemia in the US and Europe (90% of cases). CLL and Small Lymphocytic Lymphoma (SLL) are considered the same entity - CLL when predominantly leukemic, SLL when predominantly nodal.

Rare below 40 years; most cases >60 years
Male:Female ratio >2:1
Onset insidious, commonly discovered incidentally
Henry's Clinical Diagnosis and Management by Laboratory Methods

Clinical Features

Painless lymphadenopathy (diffuse)
Hepatosplenomegaly
Fatigue, weight loss, recurrent infections (hypogammaglobulinemia)
Autoimmune hemolytic anemia or ITP in 10-25%
WBC: markedly elevated, predominantly small mature lymphocytes with "smudge cells" on blood smear

Morphology

Diffuse infiltrates of small mature lymphocytes with clumped chromatin and scant cytoplasm
Admixed prolymphocytes and proliferation centers (pseudofollicles) - characteristic
Mitotic rates: very low
Smudge (smear) cells on peripheral smear: pathognomonic

Immunophenotype (Critical for Diagnosis)

B-cell markers: CD19+, CD20+(dim), CD79a+
Dim surface Ig (monoclonal IgM or IgM + IgD)
CD5+ (T-cell marker aberrantly expressed: key feature distinguishing from other B-cell lymphomas)
CD23+, CD200+, LEF1+
CD10-, BCL6-, Cyclin D1- (distinguishes from follicular and mantle cell lymphomas)

Cytogenetics & Prognostic Markers

Abnormality	Frequency	Prognosis
del(13q14.3)	50%	Favorable
Trisomy 12	20%	Intermediate
del(11q22-23) (ATM)	20%	Adverse
del(17p13) (TP53)	10%	Adverse
del(6q21)	5%	Adverse

IGHV mutation status: Mutated IGHV = better prognosis; Unmutated IGHV (ZAP-70+) = adverse prognosis
Other adverse factors: CD38+, CD49d+, lymphocyte doubling time <12 months, elevated β₂-microglobulin

Differential Diagnosis Between the Four Leukemias

Step-by-Step Approach

Step 1: Acute vs. Chronic

	Acute (AML/ALL)	Chronic (CML/CLL)
Blasts in BM	≥20%	<10% (CML chronic phase) or absent (CLL)
Onset	Abrupt, weeks	Insidious, months-years
WBC differential	Blasts predominate	Mature/maturing cells predominate
Clinical urgency	Medical emergency	Often incidental finding

Step 2: Myeloid vs. Lymphoid

Feature	Myeloid (AML, CML)	Lymphoid (ALL, CLL)
Auer rods	Present (AML)	Absent
MPO/Sudan Black	Positive	Negative
Cytochemistry	NSE+ (monocytic AML)	Negative
Flow cytometry	CD13, CD33, CD117, MPO	CD19, CD10, CD3, TdT
LAP score	Low (CML)	Normal/variable

Step 3: Within acute leukemias (AML vs. ALL)

	AML	ALL
Auer rods	Present (pathognomonic)	Absent
Cell size	Larger; more cytoplasm	Smaller; scant cytoplasm
Nucleoli	2-4, prominent	1-2, less prominent
MPO	Positive	Negative
TdT	Usually negative	Positive
CD markers	CD13, CD33, CD117, CD34	CD19/CD10 (B-ALL); CD3/CD7 (T-ALL)
Age preference	Adults (>60 yrs)	Children (peak 2-3 yrs)
Mediastinal mass	Absent	T-ALL only

Step 4: Within chronic leukemias (CML vs. CLL)

	CML	CLL
Cell type	Myeloid (neutrophils + precursors)	Lymphoid (small B lymphocytes)
Philadelphia chromosome	Positive	Negative
BCR::ABL1	Positive	Negative
LAP score	Low	Normal
Basophilia	Prominent	Absent
Smudge cells	Absent	Present
CD5+ B cells	No	Yes
Splenomegaly	Massive	Moderate
Lymphadenopathy	Mild	Prominent
Auer rods	Absent (unless blast crisis)	Absent

Differential Diagnosis from Other Conditions

AML vs. Leukemoid Reaction

	AML	Leukemoid Reaction
Auer rods	Present	Absent
LAP score	Variable (low in CML)	High
Blast count	≥20%	<5%
Philadelphia chr	Negative	Negative
Cause	Neoplastic	Infection/inflammation

CLL vs. Other Small B-Cell Lymphomas

	CLL/SLL	Mantle Cell	Follicular	Marginal Zone
CD5	+	+	-	-
CD23	+	-	-	-
CD10	-	-	+	-
Cyclin D1	-	+	-	-
LEF1	+	-	-	-
t(11;14)	Absent	Present	Absent	Absent

ALL vs. Lymphoblastic Lymphoma

Same disease - differentiated only by degree of BM involvement
>25% blasts in BM = leukemia; <25% = lymphoma (by convention)

Quick Memory Mnemonics

AML: Auer rods, Myeloperoxidase+, Middle-aged to elderly, Marrow failure presentation
ALL: All children (most common childhood cancer), Absent Auer rods, Anterior mediastinal mass (T-ALL), ACALLA (CD10)+
CML: Chromosome 9+22 (Philadelphia), Chronic course with 3 phases, Causes massive spleen, Cured by imatinib
CLL: CD5+ B-cells, Clumped chromatin, Common in elderly men, Crushed smudge cells

Treatment Summary

Leukemia	First-line	Notes
AML	Cytarabine + anthracycline ("7+3")	APL (M3): ATRA + arsenic trioxide; IDH inhibitors for mutated IDH1/2
ALL	Multi-agent chemotherapy (CALGB/GRAALL protocols)	Ph+ ALL adds imatinib/dasatinib; CNS prophylaxis essential
CML	Imatinib (1st gen TKI)	Nilotinib/dasatinib (2nd gen) for resistance/intolerance; T315I: ponatinib
CLL	Ibrutinib (BTK inhibitor), venetoclax (BCL-2 inhibitor), FCR	Watch-and-wait for early-stage; del(17p)/TP53 mutation requires ibrutinib/venetoclax

Sources:

Robbins, Cotran & Kumar Pathologic Basis of Disease (9780443264528)
Henry's Clinical Diagnosis and Management by Laboratory Methods (9780323673204)
Tietz Textbook of Laboratory Medicine, 7th Edition (9780323775724)
Quick Compendium of Clinical Pathology, 5th Edition (9780891896852)
Swanson's Family Medicine Review (9780323698115)
Goldman-Cecil Medicine (9780323930345)

AML , ALL , CML , CLL DIFFERENT AND DIFFERENTIAL DIAGNOSIS.

The comprehensive answer I just provided covers exactly this topic in full detail. Here is a complete summary for quick reference:

AML · ALL · CML · CLL — Differences & Differential Diagnosis

1. Quick Orientation: The 2×2 Framework

              ACUTE                    CHRONIC
MYELOID    AML (blasts ≥20%)         CML (Ph chromosome)
LYMPHOID   ALL (blasts ≥20%)         CLL (mature B cells)

2. Individual Disease Profiles

AML — Acute Myeloid Leukemia

Feature	Detail
Cell of origin	Myeloid progenitor (maturation arrested)
Age	Adults; median age 60 years (most common acute leukemia in adults)
Onset	Abrupt - days to weeks
Presentation	Fever, mouth ulcers (granulocyte failure), pallor, bleeding; spleen/lymph nodes NOT prominently enlarged
WBC	Variable - can be high, normal, or low
Blast count	≥20% myeloblasts in BM/blood
Pathognomonic finding	Auer rods (eosinophilic needle-like cytoplasmic inclusions)
Cytochemistry	MPO+, Sudan Black B+, chloroacetate esterase+
Immunophenotype	CD13+, CD33+, CD117+, MPO+, TdT- (usually)
Key genetics	t(15;17) APL = ATRA-sensitive; t(8;21), inv(16) = favorable; NPM1 mutation = favorable; FLT3-ITD, TP53 = poor
DIC risk	APL [t(15;17)] - hematologic emergency
Treatment	Cytarabine + anthracycline ("7+3"); ATRA + arsenic for APL
Prognosis	Variable; ~70% remission in fit patients; very poor in elderly

ALL — Acute Lymphoblastic Leukemia

Feature	Detail
Cell of origin	Immature B-cell precursor (85%) or T-cell precursor (15%)
Age	Most common cancer in children (peak 2-3 yrs); also occurs in adults (worse prognosis)
Onset	Abrupt
Presentation	Fever, bone pain, pallor, prominent lymphadenopathy + hepatosplenomegaly; T-ALL → anterior mediastinal mass; testicular involvement possible
WBC	Variable - elevated, normal, or low + neutropenia, anemia, thrombocytopenia
Blast count	≥20% lymphoblasts in BM
Auer rods	Absent (critical distinction from AML)
Cytochemistry	MPO negative; PAS+ (B-ALL); acid phosphatase+ (T-ALL)
Immunophenotype	B-ALL: CD19+, CD10+ (CALLA), CD22+, TdT+, CD34+
	T-ALL: CD3+, CD7+, TdT+, CD34+
Key genetics	Hyperdiploidy (>50 chr) = good; Hypodiploidy = poor; t(9;22) Ph+ = poor (25% adult ALL); t(12;21) ETV6::RUNX1 = excellent (childhood); NOTCH1 (T-ALL)
CNS	CNS prophylaxis essential; CNS involvement common
Treatment	Multi-agent chemo; Ph+ ALL adds imatinib/dasatinib
Prognosis	Children: 95% remission, 80% cure; adults: ~40% cure

CML — Chronic Myeloid Leukemia

Feature	Detail
Cell of origin	Myeloid stem cell
Age	45-55 years; gradual increase with age
Defining lesion	Philadelphia chromosome t(9;22)(q34;q11) → BCR::ABL1 fusion → constitutive tyrosine kinase activity (p210)
Onset	Insidious; often discovered incidentally
Presentation	Fatigue, massive splenomegaly, weight loss, night sweats; mild lymphadenopathy
WBC	Markedly elevated (50,000-200,000/µL) with full myeloid spectrum
Peripheral smear	All stages of myeloid maturation; myelocyte "bulge"; basophilia + eosinophilia + thrombocytosis
Blasts	<10% (chronic phase)
LAP score	LOW (key test - distinguishes from leukemoid reaction)
BM	Hypercellular; "dwarf" megakaryocytes; thickened paratrabecular cuff
Auer rods	Absent (unless blast crisis)

Three Phases of CML

Phase	Blasts	Key Features
Chronic	<10%	Manageable; responds well to TKI
Accelerated	10-19%	Basophilia >20%; cytogenetic progression; thrombocytopenia
Blast Crisis	≥20%	Becomes acute leukemia; 70% AML type, 30% ALL type

Treatment	Notes
Imatinib (1st gen TKI)	Competes at ATP binding site of BCR::ABL; also active vs PDGFR, c-KIT
Nilotinib, Dasatinib	2nd generation; for resistance/intolerance
Ponatinib	For T315I "gatekeeper" mutation
MRD monitoring	Quantitative RT-PCR for BCR::ABL1 transcript

CLL — Chronic Lymphocytic Leukemia

Feature	Detail
Cell of origin	Mature monoclonal B-lymphocyte (naïve B-cell phenotype)
Age	>60 years; rare <40 years; M:F > 2:1
Onset	Very insidious; often found on routine CBC
Presentation	Painless diffuse lymphadenopathy, hepatosplenomegaly, recurrent infections, fatigue; autoimmune hemolytic anemia in 10-25%
WBC	Markedly elevated - predominantly small mature lymphocytes
Peripheral smear	Monotonous small lymphocytes + smudge (smear) cells - pathognomonic
Blasts	Rare
Morphology	Small lymphocytes with clumped chromatin, scant cytoplasm; proliferation centers (pseudofollicles) in lymph nodes/BM

CLL Immunophenotype (Critical for Diagnosis)

Marker	CLL	Meaning
CD5+	Positive	Aberrant T-cell marker on B-cells - KEY feature
CD23+	Positive	Distinguishes from Mantle Cell
CD200+, LEF1+	Positive	Distinguishes from other B-cell NHL
CD20+	Dim	Weak expression
Surface Ig	Dim/monoclonal	IgM ± IgD
CD10-	Negative	Distinguishes from follicular lymphoma
Cyclin D1-	Negative	Distinguishes from mantle cell

CLL Cytogenetic Prognostic Markers

Abnormality	Frequency	Prognosis
del(13q14.3)	50%	Favorable
Trisomy 12	20%	Intermediate
del(11q22-23) [ATM]	20%	Adverse
del(17p13) [TP53]	10%	Very adverse
del(6q21)	5%	Adverse

IGHV unmutated + ZAP-70+ = aggressive course
Treatment: ibrutinib (BTK inhibitor), venetoclax (BCL-2 inhibitor), FCR; watch-and-wait for Rai stage 0-II without symptoms

3. Side-by-Side Differential Diagnosis

Step 1 — Acute vs. Chronic (First split)

Feature	Acute (AML/ALL)	Chronic (CML/CLL)
BM blasts	≥20%	<10% or absent
Onset	Abrupt (days-weeks)	Insidious (months-years)
Emergency?	Yes	Rarely
Mature cells on smear	Few	Predominant
Symptoms at diagnosis	Severe	Often none

Step 2 — Myeloid vs. Lymphoid (Second split)

Feature	Myeloid (AML, CML)	Lymphoid (ALL, CLL)
Auer rods	AML: Present	Absent always
MPO / Sudan Black	Positive	Negative
TdT	Negative (usually)	Positive (ALL)
CD3/CD19/CD20	Negative	Positive
CD13/CD33/CD117	Positive	Negative
Philadelphia chr	CML: Positive	ALL: 25% adult cases
Basophilia	CML: prominent	Absent
Smudge cells	Absent	CLL: Present

Step 3 — AML vs. ALL (Acute leukemias)

Feature	AML	ALL
Auer rods	Present - pathognomonic	Absent
MPO	Positive	Negative
TdT	Negative	Positive
Cell size	Large; more cytoplasm	Small; scant cytoplasm
Nucleoli	2-4, prominent	1-2, less prominent
CD markers	CD13, CD33, CD117, CD34	CD19/CD10 (B) or CD3/CD7 (T)
Age	Adults (>60 yrs)	Children (peak 2-3 yrs)
Mediastinal mass	Absent	T-ALL only
Hepatosplenomegaly	Mild	Prominent
Lymphadenopathy	Mild	Prominent
Gingival hypertrophy	AML-M5 (monocytic)	Absent

Step 4 — CML vs. CLL (Chronic leukemias)

Feature	CML	CLL
Cell type	Myeloid (all stages)	Mature B lymphocytes
Philadelphia chromosome	Positive	Negative
BCR::ABL1 PCR	Positive	Negative
LAP score	Low	Normal
Basophilia	Prominent	Absent
Smudge cells	Absent	Present
CD5+ B-cells	No	Yes
WBC morphology	Full myeloid spectrum	Monotonous small lymphocytes
Splenomegaly	Massive	Moderate
Lymphadenopathy	Mild	Diffuse, prominent
Auer rods	Absent	Absent
Thrombocytosis	Common	Absent (thrombocytopenia late)

Step 5 — CML vs. Leukemoid Reaction

Feature	CML	Leukemoid Reaction
LAP score	Low	High
Philadelphia chromosome	Positive	Negative
Basophilia	Present	Absent
Blasts	Present	Rare
Cause	Neoplastic	Infection/sepsis/inflammation
Toxic granulation	Absent	Present

Step 6 — CLL vs. Other Small B-Cell Lymphomas

Marker	CLL/SLL	Mantle Cell	Follicular	Marginal Zone
CD5	+	+	-	-
CD23	+	-	-	-
CD10	-	-	+	-
Cyclin D1	-	+	-	-
LEF1	+	-	-	-
t(11;14)	Absent	Present	Absent	Absent
t(14;18)	Absent	Absent	Present	Absent

4. Memory Mnemonics

Leukemia	Mnemonic
AML	Auer rods + MPO+ + Mature patients + Marrow failure
ALL	All children + Absent Auer rods + Anterior mediastinum (T-ALL) + ACALLA (CD10+)
CML	Chromosome 22 (Ph) + Chronic 3-phase course + Colossal spleen + Cured by imatinib
CLL	CD5+ B-cells + Clumped chromatin + Crushed smudge cells + Common in old men

5. Key Diagnostic Tests Ordered in Sequence

Suspected leukemia
        ↓
CBC + peripheral smear
        ↓
Is patient acute (sick, blasts on smear) or chronic (incidental)?
        ↓                              ↓
  ACUTE: BM aspirate              CHRONIC: Flow cytometry
  (blast count, morphology)       (immunophenotype)
        ↓                              ↓
  MPO/TdT/flow cytometry         Ph chromosome / BCR-ABL PCR
        ↓                              ↓
  AML if MPO+/Auer rods         CML if Ph+ / BCR-ABL+
  ALL if TdT+/MPO-              CLL if CD5+CD23+B-cells
        ↓                              ↓
  Cytogenetics + molecular      FISH for del13q, del17p
  (prognostication + Rx)        IGHV mutation status

Sources: Robbins Pathologic Basis of Disease · Henry's Clinical Diagnosis & Management · Tietz Textbook of Laboratory Medicine · Quick Compendium of Clinical Pathology · Goldman-Cecil Medicine

FMGE exam questions AML ALL CML CLL

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FMGE exam questions AML ALL CML CLL leukemia MCQ previous year

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AML ALL CML CLL leukemia MCQ questions answers

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FMGE High-Yield MCQs: AML · ALL · CML · CLL

Exam pattern note: FMGE tests leukemias through clinical vignettes, pathognomonic findings, genetic markers, and drug mechanisms. The questions below are modeled on actual FMGE/NExT previous year patterns.

SECTION A: AML — Acute Myeloid Leukemia

Q1. A 15-year-old boy presents with bleeding gums, subconjunctival hemorrhage, and purpuric rash. CBC shows Hb 6.4 g/dL, TLC 26,500/mm³, platelets 35,000/mm³. Prothrombin time is prolonged. Peripheral smear shows myeloblasts. What is the MOST LIKELY subtype?

A. Myeloblastic leukemia without maturation (M1)
B. Myeloblastic leukemia with maturation (M2)
C. Acute Promyelocytic Leukemia (M3) ✓
D. Myelomonocytic leukemia (M4)

Explanation: Bleeding + prolonged PT + myeloblasts = DIC → classic for APL (M3). DIC occurs because the abnormal promyelocytes release procoagulant tissue factor. The t(15;17) PML::RARA mutation is the hallmark.

Henry's Clinical Diagnosis & Management by Laboratory Methods

Q2. Which of the following is PATHOGNOMONIC for AML?

A. Smudge cells
B. Philadelphia chromosome
C. Auer rods ✓
D. Hyperdiploidy

Explanation: Auer rods are eosinophilic, needle-like cytoplasmic inclusions derived from MPO-positive primary granules. They are pathognomonic for AML and are NEVER seen in ALL (with rare ETP-ALL exception).

Robbins Pathologic Basis of Disease

Q3. A patient with AML is started on a drug that causes differentiation of malignant promyelocytes into mature neutrophils. The drug is acting on which translocation?

A. t(9;22)
B. t(8;21)
C. inv(16)
D. t(15;17) ✓

Explanation: ATRA (All-Trans Retinoic Acid) overcomes the differentiation block caused by the PML-RARα fusion protein in APL [t(15;17)], forcing abnormal promyelocytes to mature. This is the basis of the "differentiation therapy" paradigm.

Q4. The MINIMUM blast percentage in bone marrow required to diagnose AML is:

A. 5%
B. 10%
C. 20% ✓
D. 30%

Explanation: WHO criteria require ≥20% blasts in bone marrow or peripheral blood to diagnose AML. (Exception: if AML-defining genetics like t(15;17), t(8;21), inv(16) are present, diagnosis is made regardless of blast count.)

Q5. In AML, which marker is detected by flow cytometry that confirms MYELOID lineage?

A. CD19
B. TdT
C. CD33 / CD13 / MPO ✓
D. CD10

Explanation: CD13, CD33, CD117, and MPO are myeloid markers. TdT and CD19/CD10 are lymphoid (B-ALL). This distinction is the foundation of the AML vs. ALL differential.

Q6. A patient with AML has gingival hypertrophy, skin infiltrates, and a very high monocyte count. Which FAB subtype is MOST LIKELY?

A. M1
B. M2
C. M3
D. M4/M5 (Monocytic/Myelomonocytic) ✓

Explanation: Gingival hypertrophy is characteristic of M4 (myelomonocytic) and M5 (monocytic) AML due to tissue infiltration by monocytes/monoblasts. These cells are NSE (non-specific esterase) positive.

Q7. The BEST PROGNOSIS in AML is associated with which cytogenetic finding?

A. del(17p) / TP53 mutation
B. FLT3-ITD mutation
C. t(15;17) PML::RARA ✓
D. KMT2A (11q23) rearrangement

Explanation: APL with t(15;17) has a "Very favorable" prognosis because ATRA + arsenic trioxide achieves >90% long-term cure rates. FLT3-ITD and TP53 mutations carry the worst prognosis.

SECTION B: ALL — Acute Lymphoblastic Leukemia

Q8. ALL is MOST COMMON in which age group?

A. Neonates
B. Children aged 2-5 years ✓
C. Young adults 20-30 years
D. Elderly >60 years

Explanation: ALL is the most common cancer of childhood, peaking at 2-3 years of age. It accounts for ~25% of all childhood malignancies.

Swanson's Family Medicine Review

Q9. A 4-year-old presents with bone pain, pallor, and lymphadenopathy. Bone marrow biopsy shows sheets of small cells with scant cytoplasm and fine chromatin. MPO is NEGATIVE. TdT is POSITIVE. Diagnosis?

A. AML
B. ALL ✓
C. CML
D. CLL

Explanation: TdT+ (Terminal deoxynucleotidyl transferase) is the hallmark of ALL lymphoblasts. MPO negativity excludes AML. Scant cytoplasm and fine chromatin with prominent lymphadenopathy in a child strongly favors ALL.

Q10. The BEST PROGNOSIS in childhood ALL is associated with:

A. t(9;22) Philadelphia chromosome
B. Hypodiploidy (<46 chromosomes)
C. Hyperdiploidy (>50 chromosomes) ✓
D. KMT2A rearrangement

Explanation: Hyperdiploidy (>50 chromosomes) in B-ALL carries the best prognosis in childhood ALL. Hypodiploidy carries the worst prognosis. t(9;22) / Philadelphia chromosome in ALL (25% of adult ALL) carries poor prognosis and requires TKI addition.

Q11. A 16-year-old male presents with anterior mediastinal mass + lymphoblasts in bone marrow. The MOST LIKELY diagnosis is:

A. Hodgkin's lymphoma
B. T-cell ALL ✓
C. B-cell ALL
D. CML blast crisis

Explanation: T-ALL typically presents in adolescent males with a thymic (anterior mediastinal) mass. T-ALL cells express CD3, CD7, TdT. B-ALL does NOT produce a mediastinal mass.

Q12. The immunophenotype of B-ALL is:

A. CD3+, CD7+, TdT+
B. CD19+, CD10+, TdT+, MPO- ✓
C. CD13+, CD33+, MPO+
D. CD5+, CD23+, surface Ig dim

Explanation: B-ALL = CD19+ (B-cell), CD10+ (CALLA = Common Acute Lymphoblastic Leukemia Antigen), TdT+, MPO-. CD10 positivity is one of the most tested markers in FMGE. (Option D describes CLL.)

Q13. Which translocation in childhood ALL carries an EXCELLENT prognosis?

A. t(9;22) BCR::ABL1
B. KMT2A rearrangement
C. t(12;21) ETV6::RUNX1 ✓
D. t(1;19) PBX1::TCF3

Explanation: t(12;21) / ETV6::RUNX1 is the most common translocation in childhood B-ALL (~25%) and carries an excellent prognosis (~90% cure rate). It cannot be detected by standard karyotype - requires FISH or PCR.

Q14. CNS prophylaxis is a critical part of ALL treatment because:

A. The blood-brain barrier concentrates drugs in the CSF
B. Leukemic blasts can sanctuary in the CNS and cause relapse ✓
C. ALL arises in the leptomeninges
D. Chemotherapy is ineffective in all tissues

Explanation: The CNS is a pharmacological sanctuary - many chemotherapy agents cannot cross the blood-brain barrier effectively, allowing residual blasts to survive and cause CNS relapse. Intrathecal methotrexate is the cornerstone of CNS prophylaxis.

SECTION C: CML — Chronic Myeloid Leukemia

Q15. A 30-year-old male complains of fatigue for 1 year. He has massive splenomegaly. CBC: TLC = 1,50,000/µL with 60% neutrophils, 6% basophils, 4% eosinophils, myeloblasts + myelocytes + metamyelocytes present. The MOST LIKELY diagnosis is:

A. ALL
B. AML
C. CML ✓
D. CLL

Explanation: This is a classic FMGE/PYQ-confirmed question. The triad of massive splenomegaly + markedly elevated WBC + full myeloid spectrum (myelocyte bulge) + basophilia/eosinophilia in a young adult = CML. Confirmed by Philadelphia chromosome/BCR::ABL1 PCR.

PrepLadder FMGE PYQ (Actual previous year question)

Q16. "College girl appearance" / "Garden party appearance" of leucocytes on peripheral smear is seen in:

A. CLL
B. ALL
C. AML
D. CML ✓

Explanation: The peripheral smear in CML shows leukocytes at all stages of maturation - from myeloblasts to mature neutrophils - described as a "garden party / college girl appearance" because all age groups (maturation stages) are present.

PrepLadder FMGE PYQ (Actual previous year question)

Q17. The Philadelphia chromosome is formed by:

A. Trisomy of chromosome 22
B. Deletion of chromosome 9
C. Reciprocal translocation t(9;22)(q34;q11) ✓
D. Inversion of chromosome 16

Explanation: The Philadelphia chromosome is the first reproducible chromosomal abnormality identified in human malignancy. The t(9;22) moves the ABL1 gene on chromosome 9 adjacent to BCR on chromosome 22, producing the BCR::ABL1 constitutively active tyrosine kinase (p210).

Q18. The LAP (Leukocyte Alkaline Phosphatase) score in CML is:

A. Low / decreased ✓
B. Elevated
C. Normal
D. Absent

Explanation: Low LAP score is a hallmark of CML and is the key test distinguishing CML from leukemoid reaction (where LAP is HIGH). In blast crisis of CML, LAP may rise. This is one of the most frequently tested CML facts in FMGE.

Q19. Imatinib (Gleevec) acts by:

A. Alkylating DNA
B. Inhibiting topoisomerase II
C. Competitive inhibition of the ATP-binding site of BCR::ABL tyrosine kinase ✓
D. Blocking thymidylate synthase

Explanation: Imatinib is the prototype targeted therapy for CML. It competitively inhibits the ATP-binding site of BCR::ABL kinase, preventing phosphorylation of downstream substrates. Also active against PDGFR and c-KIT.

Katzung's Basic and Clinical Pharmacology

Q20. A CML patient on imatinib develops resistance. Sequencing shows a T315I mutation in BCR::ABL. The drug of choice is:

A. Dasatinib
B. Nilotinib
C. Bosutinib
D. Ponatinib ✓

Explanation: The T315I "gatekeeper mutation" confers resistance to ALL first- and second-generation TKIs (imatinib, nilotinib, dasatinib, bosutinib). Ponatinib (3rd gen) is the only TKI active against T315I.

Q21. In CML blast crisis, what PERCENTAGE of blasts in the bone marrow is required?

A. >10%
B. >15%
C. >20% ✓
D. >30%

Explanation: CML blast crisis is defined as ≥20% blasts in blood or bone marrow, OR a tissue infiltrate of blasts (chloroma). At this stage, CML behaves like acute leukemia - 70% AML-type, 30% ALL-type.

Q22. Minimal Residual Disease (MRD) monitoring in CML in remission is done by:

A. Conventional cytogenetics (karyotype)
B. FISH for BCR::ABL1
C. Quantitative RT-PCR for BCR::ABL1 transcript ✓
D. Flow cytometry for CD34

Explanation: Quantitative RT-PCR is the gold standard for MRD in CML due to its sensitivity (can detect 1 leukemic cell in 10⁵-10⁶ normal cells). A 3-log reduction (major molecular response) at 12 months predicts near-zero progression risk.

SECTION D: CLL — Chronic Lymphocytic Leukemia

Q23. Smudge cells / Basket cells on peripheral smear are MOST CHARACTERISTIC of:

A. AML
B. ALL
C. CML
D. CLL ✓

Explanation: Smudge (smear/basket) cells are fragile CLL lymphocytes that rupture during smear preparation. They are one of the most pathognomonic peripheral smear findings for CLL.

Q24. The HALLMARK immunophenotype of CLL is:

A. CD19+, CD10+, CD5-, CD23-
B. CD19+, CD5+, CD23+, surface Ig dim ✓
C. CD3+, CD5+, CD23-, TdT+
D. CD13+, CD33+, CD5-

Explanation: CLL has a unique phenotype: monoclonal B cells (CD19+) that aberrantly co-express the T-cell marker CD5, along with CD23+ and dim surface immunoglobulin. This pattern distinguishes CLL from ALL other B-cell lymphomas.

Q25. CLL is distinguished from Mantle Cell Lymphoma by:

A. CD5 expression
B. CD23+ and Cyclin D1- in CLL (vs. CD23- and Cyclin D1+ in MCL) ✓
C. IgM expression
D. Bone marrow involvement

Explanation: Both CLL and Mantle Cell Lymphoma (MCL) are CD5+ B-cell neoplasms, making this a classic trap question. Key distinction: CLL = CD23+, Cyclin D1-, LEF1+; MCL = CD23-, Cyclin D1+ [t(11;14)].

Q26. The MOST FAVORABLE cytogenetic finding in CLL is:

A. del(17p13) [TP53]
B. del(11q22) [ATM]
C. del(13q14) ✓
D. Trisomy 12

Explanation: del(13q14.3) is present in 50% of CLL cases and is associated with the best prognosis when it is the sole abnormality (median survival >10 years). del(17p) with TP53 loss carries the worst prognosis and is resistant to standard chemoimmunotherapy.

Q27. Which CLL molecular marker is associated with POOR prognosis?

A. Mutated IGHV
B. Unmutated IGHV + ZAP-70 expression ✓
C. del(13q14) as sole abnormality
D. Trisomy 12 alone

Explanation: Unmutated IGHV (naïve B-cell origin) correlates with ZAP-70 expression and an aggressive clinical course. Mutated IGHV (memory B-cell origin) carries a benign, indolent course with longer survival.

Q28. Transformation of CLL into an aggressive large B-cell lymphoma is called:

A. Reed-Sternberg transformation
B. Richter's syndrome / Richter transformation ✓
C. Sézary transformation
D. Waldenstrom transformation

Explanation: Richter's syndrome is the transformation of CLL/SLL into diffuse large B-cell lymphoma (DLBCL) in ~3-10% of cases. It carries a very poor prognosis (median survival <1 year). Clinically: sudden rapid lymph node enlargement, fever, weight loss, elevated LDH in a CLL patient.

Robbins Pathologic Basis of Disease

Q29. Autoimmune hemolytic anemia (AIHA) in CLL is mediated by:

A. NK cell activation
B. Warm IgG autoantibodies against RBCs (Coombs positive) ✓
C. Cold IgM agglutinins
D. Direct blast infiltration of red cells

Explanation: CLL disrupts normal immune function. AIHA occurs in ~10-25% of cases, typically warm-type (IgG), giving a positive Direct Coombs test. This is a treatable complication - steroids or rituximab are used.

SECTION E: COMPARISON / MIXED MCQs (Most Tested in FMGE)

Q30. A child presents with bone pain, pallor, hepatosplenomegaly, and lymphadenopathy. WBC = 80,000/µL with 90% lymphoblasts. MPO is negative. Diagnosis?

A. CML
B. CLL
C. AML
D. ALL ✓

Explanation: Children + lymphoblasts + MPO negative + hepatosplenomegaly/lymphadenopathy = classic ALL presentation. The markedly elevated WBC with 90% blasts and lymphoid phenotype makes AML (MPO+) and CML (full myeloid spectrum, not blasts) unlikely.

Q31. Which leukemia has the LOWEST LAP score?

A. AML
B. ALL
C. CML ✓
D. CLL

Explanation: Low LAP (Leukocyte Alkaline Phosphatase) score is a classic hallmark of CML. This is the KEY test to differentiate CML from a leukemoid reaction (high LAP). In ALL and CLL, LAP is normal or variable.

Q32. Auer rods are found in which condition?

A. ALL
B. CML
C. CLL
D. AML ✓

Explanation: Auer rods = AML, always. They are eosinophilic, needle-like cytoplasmic inclusions derived from fused primary granules (MPO-positive). They are pathognomonic - their presence alone identifies myeloid lineage and excludes ALL.

Q33. Philadelphia chromosome (t(9;22)) is found in which TWO leukemias?

A. AML and ALL
B. CLL and CML
C. CML (defining) and ALL (25% adult cases) ✓
D. AML and CML

Explanation: Philadelphia chromosome is DEFINING in CML (present in ~95%). It also occurs in 25% of adult ALL (Ph+ ALL), which requires addition of a TKI to chemotherapy. Ph is rare in AML (<1%) and not seen in CLL. This is a classic FMGE trap.

Q34. Which leukemia is most common in:

Condition	Leukemia
Children	ALL
Adults (>60 years)	AML
Elderly with incidental lymphocytosis	CLL
Young adult with massive splenomegaly	CML

Explanation: Age distribution is one of the MOST TESTED aspects of leukemia in FMGE. Memorize this table.

Q35. Match the peripheral smear finding to the leukemia:

Smear Finding	Leukemia
Auer rods in blast cells	AML
Smudge / basket cells	CLL
All stages of myeloid maturation (myelocyte bulge) + basophilia	CML
Lymphoblasts, scant cytoplasm, TdT+	ALL

Q36. Drug of choice for CML chronic phase:

A. Cytarabine
B. ATRA
C. Imatinib (BCR-ABL TKI) ✓
D. Fludarabine

Q37. Drug of choice for APL (AML-M3):

A. Imatinib
B. Cytarabine alone
C. ATRA + Arsenic Trioxide ✓
D. Ibrutinib

Explanation: ATRA + Arsenic trioxide (ATO) is now the standard of care for low-risk APL, achieving >90% cure rates without cytotoxic chemotherapy. ATRA induces differentiation; ATO induces differentiation AND apoptosis of APL cells.

Q38. Which leukemia is associated with MASSIVE splenomegaly as a presenting feature?

A. ALL
B. AML
C. CML ✓
D. CLL

Q39. A 65-year-old man is found incidentally to have WBC = 70,000/µL with 85% mature-appearing small lymphocytes. He feels well. Peripheral smear shows smudge cells. The MOST appropriate next investigation is:

A. Bone marrow biopsy immediately
B. Start ibrutinib
C. Flow cytometry (immunophenotyping) ✓
D. PCR for BCR::ABL1

Explanation: This is classic CLL. The gold standard for diagnosis and confirmation is flow cytometry showing CD5+/CD19+/CD23+/dim surface Ig B-cells. Treatment is NOT started immediately in early-stage asymptomatic CLL (watch-and-wait policy).

Q40. The Rai staging of CLL - which stage carries the WORST prognosis?

A. Stage 0 (lymphocytosis only)
B. Stage I (+ lymphadenopathy)
C. Stage II (+ splenomegaly)
D. Stage IV (+ thrombocytopenia) ✓

Explanation: Rai Stage IV = lymphocytosis + thrombocytopenia (or Stage III = anemia). These advanced stages indicate bone marrow failure and carry the worst prognosis. Stage 0 (lymphocytosis alone) = best prognosis, watch-and-wait.

RAPID-FIRE FMGE RECALL TABLE

High-Yield Point	Answer
Most common acute leukemia in children	ALL
Most common acute leukemia in adults	AML
Most common chronic leukemia in US/Europe	CLL
Pathognomonic finding of AML	Auer rods
Pathognomonic finding of CLL on smear	Smudge cells
Defining marker of CML	Philadelphia chromosome t(9;22)
Low LAP score	CML
High LAP score	Leukemoid reaction
CD10 (CALLA) + leukemia	B-ALL
TdT+ leukemia	ALL
CD5+ B-cell leukemia	CLL
AML associated with DIC	APL (M3) t(15;17)
Treatment of APL	ATRA + Arsenic trioxide
Treatment of CML	Imatinib
T315I mutation → resistant to imatinib	Use Ponatinib
CML transforms to acute leukemia	Blast crisis (>20% blasts)
CLL transforms to DLBCL	Richter's syndrome
Anterior mediastinal mass + leukemia	T-ALL
Garden party / College girl smear	CML
Worst prognosis AML	TP53 mutation / complex karyotype
Best prognosis AML	APL t(15;17)
Best prognosis ALL	Hyperdiploidy (>50 chr)
Worst prognosis ALL	Hypodiploidy; Ph+ ALL
Best prognosis CLL (cytogenetics)	del(13q14)
Worst prognosis CLL (cytogenetics)	del(17p13) TP53
Gingival hypertrophy in leukemia	AML M4/M5 (monocytic)
Testicular involvement in leukemia	ALL

Sources: PrepLadder FMGE PYQs · Robbins Pathologic Basis of Disease · Henry's Clinical Diagnosis & Management · Katzung's Basic and Clinical Pharmacology · Goldman-Cecil Medicine · Quick Compendium of Clinical Pathology

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