Category Archives: Bone Marrow

Organ Systems, Bone Marrow, WHO Classification

Myeloproliferative Neoplasm – Unclassifiable (MPN-U)

Immunohistochemistry
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited.  Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia.  Helpful IHC markers may include:
 
Stain
Comment
CD34 marks immature cells including myeloblasts.  In the setting of AML, it is ~70% sensitive.  A subset of lymphoblasts may express CD34.
CD117 is a specific myeloid marker, and marks a subset of myeloblasts.  The expression is dim, and one often must look at 20-40X to clearly see expression.  Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells.  This may be helpful in quantitating and differentiating erythroid cells from myeloid cells.  This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells.  Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker.  It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).  
References
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.
Organ Systems, Bone Marrow, WHO Classification

Mast Cell Disease (Mastocytosis)

Mastocytosis is a clonal (neoplastic) proliferation of mast cells.  It can be a heterogeneous disorder ranging from skin lesion, which spontaneously regress, to aggressive systemic disease with a short survival.  Mastocytosis is divided into two generalized categories:  cutaneous mastocytosis (CM) and systemic mastocytosis (SM).  CM is limited strictly to the skin, but SM has at least one extracutaneous organ involved (+/- skin involvement).
 
In SM the bone marrow is almost always involved.  Approximately 50% of SM patients will have skin involvement.
Cutaneous Mastocytosis
  • Diffuse Cutaneous Mastocytosis
  • Mastocytoma of Skin
  • Urticaria Pigmentosa (UP)/Maculopapular Cutaneous Mastocytosis (MPCM)
Systemic Mastocytosis
  • Indolent Systemic Mastocytosis
  • Systemic Mastocytosis with associated clonal hematological non-mast cell lineage disease (SM-AHNMD)
  • Aggressive Systemic Mastocytosis (ASM)
  • Mast Cell Leukemia
  • Mast Cell Sarcoma
  • Extracutaneous Mastocytoma
Immunohistochemistry
Stain
Comment
CAE
Strongly reactive (must be used in combination with MPO)
MPO
Negative
Tryptase
Positive, not specific.  Positivity of spindle cells in the bone marrow (BM) is considered specific for mast cells.  Positivity of round cells in the BM may represent one of three entities: (1) mast cells (CD117+, chymase +), (2) neoplastic basophils, or (3) AML.
Chymase
Subset Positive (highly specific but not sensitive)
Positive
Expressed in a subset of neoplastic mast cells (specific).  Must differentiate from T-cells.
Expressed in a subset of neoplastic mast cells (specific).  Must differentiate from T-cells.  Commonly expressed in neoplastic mast cells involving the GI tract.
CD9
Positive
Positive
Positive
Positive
Negative
CD14
Negative
CD16
Negative
Reticulin
In systemic mastocytsis with bone marrow involvement, there is often significant reticulin fibrosis.
CAE – Naphthphol-ASD-Chloroacetate Esterase, MPO – Myeloperoxidase
Photomicrographs
Systemic Mastocytosis - CD117
Systemic Mastocytosis – CD117
Systemic Mastocytosis - H&E
Systemic Mastocytosis – H&E
References
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.
Organ Systems, Bone Marrow, WHO Classification

Chronic Eosinophilic Leukemia (CEL)

Immunohistochemistry
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited.  Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia.  Helpful IHC markers may include:
 
Stain
Comment
CD34 marks immature cells including myeloblasts.  In the setting of AML, it is ~70% sensitive.  A subset of lymphoblasts may express CD34.
CD117 is a specific myeloid marker, and marks a subset of myeloblasts.  The expression is dim, and one often must look at 20-40X to clearly see expression.  Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells.  This may be helpful in quantitating and differentiating erythroid cells from myeloid cells.  This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells.  Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker.  It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).  
References
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.
Organ Systems, Bone Marrow, WHO Classification, MPN

Essential Thrombocythemia (ET)

Major Criteria
  1. Platelet count ≥450,000/μL 
  2. Presence of JAK2, CALR, or MPL mutation
  3. Does not meet the WHO criteria for another myeloid neoplasm
  4. BM biopsy showing megakaryocytic proliferation
    • Enlarged mature megakaryocytes
    • Hyperlobated nuclei (not as pleomorphic or bizzare as in PMF)
    • Granulopoiesis and erythropoiesis is not increased or left shifted
    • No more than MF1 reticulin fibrosis
Minor Criteria
  • Evidence of a clonal marker or exclusion of reactive thrombocytosis

Diagnosis of ET is confirmed by all four major criteria, or if there is no evidence of a JAK2, CALR, or MPL mutation (major criterion #2), then the presence of the minor criterion.

Frequency of Molecular Abnormalities
  • JAK2 – 63% (V617F mutation)
  • CALR – 18%
  • MPL – 2-3%

Overall, approximately 83% of cases of ET have either a JAK2, CALR, or MPL mutation (n=79).

Photomicrographs
Essential Thrombocytosis (ET)
Essential Thrombocytosis (ET)
Essential Thrombocytosis (ET)
Essential Thrombocytosis (ET)
Essential Thrombocytosis (ET)
Essential Thrombocytosis (ET) – Reticulin stain (MF0)
Immunohistochemistry
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited.  Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia.  Helpful IHC markers may include:
 
Stain
Comment
CD34 marks immature cells including myeloblasts.  In the setting of AML, it is ~70% sensitive.  A subset of lymphoblasts may express CD34.
CD117 is a specific myeloid marker, and marks a subset of myeloblasts.  The expression is dim, and one often must look at 20-40X to clearly see expression.  Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells.  This may be helpful in quantitating and differentiating erythroid cells from myeloid cells.  This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells.  Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker.  It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).  

 

References

Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.
 
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127: 2391–2405. doi:10.1182/blood-2016-03-643544
 
Kim SY, Im K, Park SN, Kwon J, Kim J-A, Lee DS. CALR, JAK2, and MPL mutation profiles in patients with four different subtypes of myeloproliferative neoplasms: primary myelofibrosis, essential thrombocythemia, polycythemia vera, and myeloproliferative neoplasm, unclassifiable. Am J Clin Pathol. 2015;143: 635–644. doi:10.1309/AJCPUAAC16LIWZMM
Bone Marrow, WHO Classification, MPN

Primary Myelofibrosis (PMF)

Major Criteria
  1. Presence of JAK2, CALR, or MPL mutation, (or) presence of other clonal marker (or) absence of reactive fibrosis
  2. Does not meet WHO criteria for another myeloid/myeloproliferative neoplasm
  3. Presence of an atypical megakaryocytic proliferation and grade 2-3 fibrosis (MF2-3)
Minor Criteria

Presence of at least one of the following on two consecutive studies:

  • Leukoerythroblastosis
  • Splenomegaly (palpable)
  • Leukocytosis (>11,000/μL)
  • Anemia (not caused by another condition)
  • Elevated LDH

Diagnosis of PMF requires meeting all three major criteria and at least one minor criteria.

Pre-fibrotic Myelofibrosis (pre-PMF)
  • Same criteria as PMF, except fibrosis is MF1 or less, and leukoerythroblastosis is not included in the minor criteria
  • In contrast the ET, pre-PMF is hypercellular for age with an increased granulocytic component (erythroid component is often decreased).
Frequency of Molecular Abnormalities
  • JAK2 – 57-58% (V617F mutations)
  • CALR – 15-25%
  • MPL – 8-9%

Overall, approximately 80-91% of cases of PMF have either a JAK2, CALR, or MPL mutation.

Myelofibrosis Grading
Grade
Comment
Scattered linear fibers without intersections.  Normal bone marrow.
MF1
Loose network of reticulin fibers with intersections (particularly perivascular)
Diffuse increase of reticulin fibers with increased density and numerous intersections.  Focal bundles of thick fibers.
Diffuse increase of reticulin fibers with increased density and numerous intersections.  Increased thick bundles of fibers consistent with collagen fibrosis.  Osteosclerosis usually present.

In cases of MF2 or MF3, it is recommended to perform trichrome stain to evaluate for collagen fibrosis.

MF – Accelerated phase = 10-19% blasts in the peripheral blood and/or the bone marrow.
MF – Acute Transformation = ≥20% blasts in the blood or bone marrow.
 
Treatment – JAK 1/2 inhibitor ruxolitinib/Jakafi®
Photomicrographs
Primary Myelofibrosis (PMF)
Primary Myelofibrosis (PMF)
Primary Myelofibrosis (PMF)
Primary Myelofibrosis (PMF)
Immunohistochemistry
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited.  Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia.  Helpful IHC markers may include:
 
Stain
Comment
CD34 marks immature cells including myeloblasts.  In the setting of AML, it is ~70% sensitive.  A subset of lymphoblasts may express CD34.
CD117 is a specific myeloid marker, and marks a subset of myeloblasts.  The expression is dim, and one often must look at 20-40X to clearly see expression.  Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells.  This may be helpful in quantitating and differentiating erythroid cells from myeloid cells.  This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells.  Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker.  It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).  
References
Swerdlow SH, Campo E, Harris, NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):  WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017
 
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127: 2391–2405. doi:10.1182/blood-2016-03-643544
 
Kim SY, Im K, Park SN, Kwon J, Kim J-A, Lee DS. CALR, JAK2, and MPL mutation profiles in patients with four different subtypes of myeloproliferative neoplasms: primary myelofibrosis, essential thrombocythemia, polycythemia vera, and myeloproliferative neoplasm, unclassifiable. Am J Clin Pathol. 2015;143: 635–644. doi:10.1309/AJCPUAAC16LIWZMM
 
Tefferi A, Lasho TL, Finke CM, Knudson RA, Ketterling R, Hanson CH, et al. CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons. Leukemia. 2014;28: 1472–1477. doi:10.1038/leu.2014.3
 
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011.
Organ Systems, Bone Marrow, WHO Classification, MPN

Chronic Myelogenous Leukemia (CML)

  • Myeloproliferative neoplasm containing the translocation t(9;22)(q34.1;q11.2) resulting in the BCR-ABL1 fusion gene, the Philadelphia chromosome (Ph).
    • 90-95% of cases have the classic translocation.
    • Small number of remaining cases may have a cryptic translocation (detected by FISH or RT-PCR).
    • p210 – major breakpoint present in most cases.
    • p230 – a larger fusion protein present in a small number of cases, which may have a more prominent neutrophilic component and/or thrombocytosis.
    • p190 – minor breakpoint, frequently associated with ALL (can be seen in rare cases of CML with increased monocytes, which mimic CMML).
  • Granulocytes are the predominate component (myelocyte bulge).
  • Tyrosine kinase inhibitor (TKI) therapy has turned CML into a chronic disease.

Continue reading Chronic Myelogenous Leukemia (CML) →

Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Mature B-Cell Neoplasms

Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL)

CLL/SLL represents a B-cell neoplasm of small lymphocytes which involve a combination of peripheral blood, bone marrow, and/or lymph nodes.  When peripheral blood predominates, then it is referred to as CLL, and when it presents as predominately nodal involvement it is referred to as SLL.  This is the same disorder with different manifestations.

Continue reading Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL) →

Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Monoclonal B-Cell Lymphocytosis (MBL)

Monoclonal B-cell lymphocytosis (MBL) was defined by the International Familial CLL consortium in 2005 as a monoclonal B-cell lymphocyte population in the peripheral blood <5,000/uL without evidence of lymphadenopathy (i.e. SLL), an autoimmune/infectious disease or other features diagnostic of a B-cell lymphoproliferative disorder.  The 2016 WHO hematopathology revision dropped the requirement of cytopenias or disease related symptoms as adequate to make the diagnosis of CLL.

Continue reading Monoclonal B-Cell Lymphocytosis (MBL) →