Acute Leukemia

Table Of Contents
  1. Overview
  2. Diagnosing Acute Leukemia
  3. Acute Lymphoblastic Leukemia
  4. Acute Myelogenous Leukemia (AML)

Overview

Acute Leukemia is an abnormal proliferation of blasts in either the peripheral myeloid or lymphoid cell lines. Acute Leukemias are of rapid onset. The blasts dramatically affect the bone marrow and consume nutrients and other resources leading to a pancytopenia. Although WBC count is high, the proliferating cells are non-functional and immature. Compared to chronic leukemias, acute leukemia is more common in younger patients. ALL is most common in children

AML accounts for 15% of leukemias in children. ALL on the other hand accounts for 80% of paediatric acute leukemias. The overall survival for children with AML is approximately 65-75%. ALL has a higher survival at more than 90% with treatment.

Hematopoiesis
Hematopoiesis
  • Classic presentation of acute leukemia
    • Fatigue, weakness, pallor (due to anemia)
    • Easy bruising and bleeding (due to thrombocytopenia)
    • Increased susceptibility to infection (due to leukopenia/non-functional leukocytes)
  • “Myeloid sandwich” Incidence increases with age (going down)
    • ALL
    • AML
    • CML
    • CLL

Diagnosing Acute Leukemia

Bone marrow biopsy is the most accurate test for diagnosing acute leukemia. > 20% blasts need to be present for the diagnosis to be made. And these blasts can be differentiate into myeloblasts or lymphoblasts based on cytochemical and immunophenotypical characteristics.

A hypercellular bone marrow
A hypercellular bone marrow
  • When is a bone marrow aspirate indicated?
    • Evaluation of anemia of unknown origin
    • Evaluation of primary hematological malignancies (Leukemia, MPD, MDS)
    • Evaluation of metastasis (Common metastasis from thyroid, breast, ovaries and prostate)
    • Evaluation of storage disorders (Gaucher disease, Niemannpick disorder)
    • Evaluation of fever of unknown origin (rule out fungal, bacterial, parasitic infections i.e. histoplasmosis and leishmaniasis)
    • Assessment of iron stores
    • Bone Marrow transplantation
  • When is a bone marrow aspirate contraindicated?
    • Severe bleeding diatheses (severe hemophilia, severe DIC)
    • Thrombocytopenia (not a contraindication, platelet transfusion can be performed, clinically warranted if the platelet count is below 20,000 cells/uL)
    • Individuals with diffuse bone resorption due to metabolic or lytic processes (multiple myeloma – aspirate the iliac crest instead of the sternum to mitigate the risk of perforating the mediastinum)
    • Sternum biopsy (even in patients with healthy bone, unless obese)
  • What instruments are used to perform bone marrow aspirates and trephine biopsy**?**
    • Trephine biopsy and aspirate: Jamshidi needle, Westerman-jensen needle
    • Bone marrow aspirate: Klimah needle, Salah needle. Has adjustable guards
  • List the sample containers used for bone marrow aspiration tests
    • EDTA: Morphology (Romanowsky staining), Molecular tests (PCR), Cytochemistry
    • **Heparin:**Cytogenetics, Immunophenotyping
  • What are the identifying features of blast cells?
    • Blasts are generally larger
    • Blasts have an increased nuclear-cytoplasm ratio,
    • Blasts have a deep-blue cytoplasmic staining (mature cells stain lighter)
    • Blasts have irregular nuclear contour
    • Blasts have immature chromatin (salt and pepper, mature chromatin is more condensed)
    • Blasts have prominent nucleoli (nucleolus)
Blast cell
Blast cell
  • What are the morphological identifying features of cells in the myeloid series?
    • Myeloblast: High nuclear-cytoplasmic ratio, immature chromatin, prominent nucleoli (3-4)
    • Promyelocyte: High-nuclear-cytoplasmic ratio (though more cytoplasm than myeloblasts), round nucleus with immature chromatin, prominent nucleoli, cytoplasm shows primary azurophilic granules
    • Myelocyte: Eccentric oval nucleus with no indentation, mature chromatin (condensed), absent nucleoli, more cytoplasm, less primary granules and more secondary azurophilic granules ***Last stage that cells can undergo mitosis in
    • Metamyelocyte: Kidney-bean-shaped nucleus with indented nucleus (note that the indentation is less than half the diameter of the nucleus), mature chromatin, only secondary granules
    • **Band form (Juvenile):**Kidney bean shaped with indented nucleus (more than half the diameter of the nucleus), more cytoplasm, secondary granules)
    • Segmented neutrophil: Mature nucleus divided into 3-5 lobes connected but thin chromatin filaments, secondary granules
Myeloid series
Myeloid series

Cytochemical identifying features of cells in the myeloid and lymphoid series

MyeloblastLymphoblast
MPOPositiveNegative
NSEDiffuse positiveNegative
CAEPositiveNegative
PASDiffuse positiveBlock positive
Sudan BlackPositiveNegative
  • Immunophenotypical identifying features of cells in the myeloid and lymphoid series
    • Lymphoblasts: TdT
      • Pan T-cell markers: CD3+, CD5+, CD7+
      • **Pan B-cell markers:**PAX-5, CD19+, CD79A+
    • Myeloblast: CD10+, CD19+, CD22+, CD34+, HLA-DR
      • AML: CD11b+, CD34+, CD33+, CD45+, CD64+, CD65+, CD117+, MPO, Lysozyme
      • Pure Erythroid Leukemia (AML-M6): CD71+, Glycophorin A positive
      • Acute Megakaryoblastic Leukemia (AML-M7): CD41+, CD61+

Acute Lymphoblastic Leukemia

ALL is a malignant neoplasm of the lymphocyte precursor cells (Pre-B and T-cells). Pre-B cells account for 88% of cases. Leukemic lymphoblasts have exaggerated and uncontrolled growth and fail to mount a normal immune response. They also cause a drop in the production of normal bone marrow cells leading to pancytopenia (and its sequale).

ALL represents <1% of adult cancers and 25% of childhood cancers. It is the most common acute leukemia in children ≤14 years (75%). Survival is inversely related to age. Children have a better survival than adults (>90% 5-year survival rate). Peak incidence is at 3-4 years, and another secondary peak at 60 years. It affects boys > girls.

  • WHO classification of ALL ***Based on morphology, cytochemistry, immunophenotyping and cytogenetics
    • Pre-B cell Leukemia or Lymphoma: 85%
      • CALLA (CD10+), CD19+, CD20+, TdT+
    • Pre-T cell Leukemia or Lymphoma: 15%
      • Common in Teenagers with a Thymic mass. Do not express CALLA (CD10)
      • CD2+, CD3+, CD4+, CD5+, CD7+, CD8+, TdT+
  • FAB classification of ALL ***Based on blast morphology and cytochemistry ****
    • ALL-L1: Precursor lymphoblasts; more common in children than in adults (85% vs 30%)
    • ALL-L2: Precursor lymphoblasts; more common in adults than in children (60% vs 15%). They are larger than the typical L1 blasts (Oval or irregular nuclear outline, less homogeneous chromatin, variable nuclei but frequently prominent, sometimes multiple, more abundant cytoplasm but still pale blue)
    • ALL-L3: more mature subtypes of B-cells (Burkitt-L3 cells)
  • Risk factors for ALL Cause is unknown. Majority of all cases are not associated with genetic or environmental risk factors.
    • Genetic and immunodeficiency syndromes
      • Down syndrome
      • Bloom syndrome
      • Neurofibromatosis type 1
      • ataxia telangiectasia*.***
    • Ionizing radiation
  • Signs and symptoms
    • Fatigue, pallor, breathlessness (due to anemia)
    • Fever and recurrent infections (due to neutropenia)
    • Spontaneous bleeding and bruising (due to thrombocytopenia)
    • Weight loss, fevers, night sweats (due to B-cell dysfunction)
    • Lymphadenopathy (due to extramedullary spread to lymph nodes)
    • Hepatsplenomegally (due to extramedullary hematopoiesis and spread to liver and spleen)
    • Painles, unilateral testicular mass (due to extramedullary spread to testes)
    • Cranial nerve palsy, Nausea, Vomiting, headache, Papilledema (due to CNS involvement → meningeal infilatration and CSF outflow obstruction)
    • Bone pains and difficulty walking, especially in young children (due to bone marrow expansion)
  • Investigations
    • Peripheral Blood Evaluation
      • CBC: Pancytopenia, decrease ANC, low Hgb <8g/dL, platelet count <150,000/mL, anemia, thrombocytopenia, normal or slightly increased WBC count
      • PBF: Lymphoblasts present (Agranular large cell, Absent Auer rods)
    • Bone Marrow Evaluation ***Biopsy provides a baseline for cellularity, degree of residual hematopoiesis, presence of necrosis or other associated features
      • Trephine Biopsy: Increased marrow cellularity (due to infiltration by densely packed blastic elements with no particular pattern of involvement), Hypocellular presentations are rare in ALL, frank fibrosis may be present but increased reticulin is more common
    • Phenotyping using cytochemical stains
      • MPO: negative
      • Sudan B Black: negative
      • Non-specific esterase (NSE): negative
      • Periodic Acid-Schiff (PAS): Block positive
      • Acid phosphatase: Focal positive
    • Immunophenotyping (Flow cytometry) ***to further subclassify cases into precursor-B cell and T-cell lineage types. It is performed from blood or BMA and surface and cytoplasmic markers are used.
      • Terminal Deoxynucleotidyl transferase (TdT): positive for both ***useful for lymphoblastic leukemia id
      • B-precursor leukemia: CD10+(CALLA) , CD19+, CD22+, TdT, Cytoplasmic CD79A, CD34, CD9a+, CD20+, lack of cytoplasmic (c) and surface immunoglobuline (sIg) expression
      • T-precursor leukemia: CD2+, CD3+, CD4+, CD5+, CD7+
    • Cytogenetic analysis ***Important for diagnosis, confirmation of subtype class and prognsis. Abnormal chromosome number or structure are seen in 90% of children and 70% of adults with ALL
      • Germ-line abnormalities: Down syndrome, Bloom Syndrome, Fanconi Anemia, Klinefelter syndrome, Ataxia-telangiectasia
      • Translocations: t(9;22), t(4;11), t(9;11). t(11;19) ***t(9;22) is th single-most frequent chromosomal abnormality in adult ALL. It is detected in 11-34% of patients with ALL and is associated with unfavourable prognosis
      • Deletions: del(6q), del(9p), t(9p)
      • Somatic abnormalities: Aneuploidy (92% of childhood ALL), Hyperdiploidy (20-30% of pre-B ALL and 90% of early pre-B ALL), Hypodiploidy (<46 chromosome found in 4-9% of adult ALL, poor prognosis), Low hyperdiploid (47-50 chromosomes), High hyperdyploid (>50 chromosomes) ***Pts with hyperdiploid cells are more sensitive than nonhyperdiploid cells to chemotherapy and show more rapid induction of apoptosis
    • Molecular evaluation ***RT-PCR is suited for analysis of translocations that result in fusion genes. Quantitatvie RT-PCR allows for quantification of minimal residual disease (MRD)
    • Lumbar puncture and CSF analysis
      • CNS involvement used by the Children’s Cancer Group: >5WBC/L of CSF with unequivocal blasts identified on the cytospin
        • CNS 1: <5 WBC/L of CSF no blasts
        • CNS 2: < WBC/L of CSF with blasts
        • CNS 3: >5 WBC/L of CSF and blasts or cranial nerve findings
    • Evaluation of Tumor Lysis Syndrome
      • Blood chemistry: Hypocalcemia, Hyperphosphatemia, Hyperkalemia, Elevated LDH, Hyperuricemia, Elevated creatinine
  • Treatment
    • Admit
    • Reverse isolation
    • Group and Crossmatch then Transfuse pRBCs
    • Broad spectrum antibiotics if needed
    • Consult hametology/oncology for induction of chemotherapy
      • Standard induction with Cyclophosphamide, Vincristin, Adriamycin and Dexamethasone (CVAD)
      • Intrathecal Methotrexate or ARA-C for CNS prophylaxis
    • Counsel and Reassure the patient
  • Differentials
    • AML: Clinically indistinguishable. MPO positive. Auer rods.
    • MDS: Bone marrow shows <20% blasts
    • Myelofibrosis: Tear drop RBCs on PBF: Bone marrow failure → massive splenomegaly due to extramedullary hematopoiesis
    • Reactive lymphocytosis: Increased but normal WBCs following viral infection. No blasts in the peripheral smear or biopsy.
    • Aplastic anemia: hypocellular bone marrow. No blasts in the peripheral smear or bone marrow biopsy. Anemia without thrombocytopenia or WBC disturbance
    • Immune thrombocytopenia: normal bone marrow. No blasts. Isolated thrombocytopenia.
  • Complications
    • Chemotherapy related adverse effects
      • Cyclophosphamide → hemorrhagic cystitis
      • Vincristine → peripheral neuropathy
      • Adriamycin → Dilated cardiomyopathy
      • Dexamethasone → cushing syndrome, bone demineralization, avascular necrosis
    • Tumor lysis syndrome: prophylaxis with Allopurinol and vigorous hydration
    • Complications related to cytopenias
Peripheral blood film showing lymphoblasts in ALL
Peripheral blood film showing lymphoblasts in ALL

Acute Myelogenous Leukemia (AML)

AML is an acute leukemia involving precursor cells committed to the myeloid cell line (granulocytic, monocytic, erythroid, megakaryocytic) – The presence of granules makes it myeloid. There is an increased risk of AML with exposure to cytotoxics/radiation and chromosomal abnormalities.

Incidence increases with age. Most patients are > 60 years.

  • WHO classification of AML This classification is based on a combination of clinical manifestations, morphology, Immunophenotyping, and genetic features. It has diagnostic and therapeutic value
    • AML with recurrent genetic abnormalities
    • AML with myelodysplasia-related features (Monosomy 5, Monosomy 7 – poor prognosis)
    • Therapy-related AML (History of alkylating agent use etc.)
    • AML, not otherwise specified (Classified further using FAB)
    • Myeloid Sarcoma
    • Myeloid proliferations related to Down Syndrome (Trisomy 21)
  • French-American-British (FAB) classification of AML The FAB classification is based on the lineage affected and level of association. It needs 30% blasts ( lowered to 20% by WHO)
    • AML with minimal differentiation (AML-M0)
    • AML without maturation (AML-M1)
    • AML with maturation (AML-M2)
    • Acute Promyelocytic Leukemia (AML-M3)
    • Acute Myelomonocytic Leukemia (AML-M4)
    • Acute Monoblastic and Monocytic leukemia (AML-M5)
    • Pure Erythroid Leukemia (AML-M6)
    • Acute Megakaryoblastic Leukemia (AML-M7)
  • Causes of AML
    • Denovo AML (DN-AML):
      • Chromosomal abnormalities: t(8:12), t(15:17) APL, t(16:16) inverted 16, Trisomy 21 (Down syndrome), MDS associated mutations that transform into AML (Monosomy 5, Monosomy 7, del(5q)).
      • Physical and chemical agent exposure: Ionizing radiation, Chemotherapeutic agents (Alkylating agents), Occupational agents (Benzene).
    • Secondary AML: occurs when MDS transforms into AML and during chemotherapy –
      • Therapy-related (Alkylating agents, Topoisomerase II inhibitors, Epipodophyllotoxins, anthracyclines, mitoxantrone)
  • Pathogenesis of AML
    • AML involves precursor cells committed to the myeloid line (granulocytic, monocytic, erythroid, megakaryocytic elements).
    • It develops as a consequence of genetic changes in hematopoietic precursor cells (commonly after chemotherapy, ionizing radiation, chemical exposure and infection with retroviruses)
    • **These genetic changes alter normal hematopoietic growth and differentiation.
    • There is a clonal proliferation of myeloid precursors with maturation arrest (inability to differentiate into more mature cellular elements**)**
    • Leukemic blasts accumulate in the bone marrow, peripheral blood and other tissue (myeloid sarcomas especially in the orbit)
    • Reduction in the normal production of RBCs, platelets and mature granuloyctes causes anemia, bleeding diathesis and increased risk of infection
  • Signs and symptoms
    • Individuals present with a pancytopenia
      • Neutropenia – recurrent infections and fever)
      • Thrombocytopenia – bleeding diathesis and recurrent bleeding
      • Anemia – fatigue, pallor, breathlessness
    • Bone pain
    • Lymphadenopathy
    • Hepatosplenomegaly (due to exramedullary hematopoiesis)
    • Orbital swelling (in myeloid sarcoma)
    • Headache
    • Lethargy
    • Mental status changes and Cranial nerve palsies (when there is CNS involvement)
  • Investigations
    • Peripheral Blood Assessment:
      • CBC: Anemia and thrombocytopenia, Decreased, normal or increased WBC
      • PBF: Myeloblasts present (Large nuclei, prominent nucleoli, variable amount of pale blue cytoplasm, presence of Auer rods and granules) ***Note that the blasts in Myeloblasts have more abundant cytoplasm than Lymphoblasts
    • Bone Marrow Evaluation:
      • BMA: 20% blasts in the Bone marrow for diagnosis, Counted against 500 nucleated cells ***acute myeloid leukemia with recurrent genetic abnormalities are diagnosed using the presence of their genetic abnormalities {t(8:21), t(15:17), t(16:16)}
      • Trephine Biopsy: Assesses marrow cellularity, Megakaryocyte distribution and morphology, presence of fibrosis and other abnormal cells ***Rules out metastases. Dry taps can occur due to a packed marrow or associated marrow fibrosis.
        • Morphology, rule out metastases
    • Phenotyping using cytochemical stains ***Note that positive cytochemical stains are helpful for diagnosis, but they do not rule out myeloid lineage
      • Myeloperoxidase (MPO): Positive for myeloblasts (Negative/weakly positive in Monoblasts and promonocytes; Negative in lymphoblasts, erythroblasts and megakaryoblasts
      • Nonspecific Esterase (NSE): positive for Monoblasts and monocytes (diffuse reactivity)
      • Specific Esterase (CAE): positive for the granulocytic lineage (from promyelocyte stage onwards, using Naphthol AS-D chloroacetate esterase (CAE)
      • A combined esterase reaction: CAE positive for granulocytic and NSE positive for monocytic lineages
      • Periodic Acid Schiff: Positive in erythroblasts and megakaryoblastic lineages (diffuse positivity)
      • Sudan Black Stain: Positive for granulated blasts
    • Flow cytometry (Immunophenotyping) ***Determined by flow cytometry or by immunohistochemistry (trephine biopsy) to distinguish AML from ALL. It determines the myeloid-specific lineage but usually does not substitute for morphological FAB classification.
      • AML: CD11b, CD34, CD33, CD45, CD64, CD65, CD117, MPO, Lysozyme
      • Pure Erythroid Leukemia (AML-M6): CD71, Glycophorin A positive
      • Acute Megakaryoblastic Leukemia (AML-M7): CD41, CD61 positive
    • Cytogenetics ***Includes Karyotyping and FISH. These cytogenetic aberrations have prognostic and therapeutic implications
      • Good prognosis: t(8;12), inv(16), t(16:16), t(15;17),
      • Poor prognosis: MDS-associated mutations (Monosomy 5, Monosomy 7, del(5q)), t(11:var) associated with therapy induced AML
    • Molecular Studies (PCR): ***Pediatric AML is genetically heterogeneous and multiple genetic mutations have therapeutic and prognostic value
      • PCR: Nucleophosmin mutation (NPM1), CEBPA, FLT3/ITD, c-KIT, WT1, PML-RARA
    • Lumbar Puncture and CSF analysis: all patients with AML + neurologic symptoms get LP + intrathecal Cytarabine. Only performed when PLT > 20,000/uL and no signs of raised ICP.
      • Lumbar puncture and CSF analysis
    • Evaluation of Tumor Lysis Syndrome ***Tumor lysis syndrome occurs in cases with high cell-turnover (Mature-B ALL or ALL-L3). These patients need to be hydrated
      • Blood chemistry: Hypocalcemia, Hyperphosphatemia, Hyperkalemia, Elevated LDH, Hyperuricemia, Elevated creatinine – have to be rehydrated
  • Treatment
    • Admit
    • Reverse isolation
    • Group and Crossmatch then Transfuse pRBCs
    • Broad spectrum antibiotics if needed
    • Consult hametology/oncology for induction of chemotherapy
      • Standard induction with Idarubicin and Cytarabine (IAC)
      • Intrathecal Cytarabine if there is CNS involvement
      • ATRA and Arsenic trioxide for AML-M3
    • Counsel and Reassure the patient
  • Differentials
    • ALL: More common in children. Bone marrow shows >20% blasts that stain positive for CALL and/or TdT. Lymphoblasts.
    • MDS: Bone marrow shows <20% blasts
    • Myelofibrosis: Tear drop RBCs on PBF: Bone marrow failure → massive splenomegaly due to extramedullary hematopoiesis
    • Reactive lymphocytosis: Increased but normal WBCs following viral infection. No blasts in the peripheral smear or biopsy.
    • Aplastic anemia: hypocellular bone marrow. No blasts in the peripheral smear or bone marrow biopsy. Anemia without thrombocytopenia or WBC disturbance
    • Immune thrombocytopenia: normal bone marrow. No blasts. Isolated thrombocytopenia.
  • Complications
    • Leukostasis: dyspnea, chest pain, headaches, altered mental status, cranial nerve palsies, or priapism
    • Chemotherapy related complications
      • ARA-C (Cytarabine) → multiple complications
      • Idarubicine → Dilated cardiomyopathy
    • Tumor lysis syndrome: prophylaxis with vigorous hydration and allopurinal
    • DIC: particularly with AML-M3
    • Complications related to cytopenias
Bone marrow biopsy showing AML
Bone marrow biopsy showing AML

Acute Promyelocytic Leukemia (APL or AML-M3)

APL is a rare subtype of AML characterized by maturation arrest at the promyelocytic stage and the classic chromosome translocation t(15:17) forming the PML-RARA fusion protein.. Cells have granules and Auer-rods.

Immature myeloblasts with linear Auer rods
Immature myeloblasts with linear Auer rods
  • Treatment
    • ATRA (ALL-trans retinoid acid) and Arsenic trioxide
  • Complications
    • Disseminated Intravascular Coagulation (auer rods activate platelets?)

Down Syndrome and Acute Megakaryoblastic Leukemia (AML-M7)

Children with Down Syndrome have 10 to 20 times greater risk of developing AML. AML in children with DS has a unique biological characteristic that greatly influences therapy and prognosis. The additional chromosome 21 is an important predisposing factor for the development of AML.

Chloromas (Myeloid Sarcomas)

Myeloid sarcoma are deposits of myeloid blasts outside the bone marrow (extramedullary) that may cause destruction or compression in normal tissue.

  • Sites of chloromas
    • CNS
    • Skin
    • Orbit
    • Bone
  • Risk factors for developing chloromas
    • Younger age
    • High WBC at diagnosis
    • t(8:21)
    • AML-M4
    • AML-M5