Bone marrow neoplastic

Bone marrow - neoplastic myeloid

Myeloproliferative neoplasms (MPN)

Chronic neutrophilic leukemia



Minor changes: 19 July 2021

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PubMed Search: Chronic neutrophilic leukemia [title] pathology


Jingwei Li, M.D., Ph.D.
Vignesh Shanmugam, M.D.
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Cite this page: Li J, Shanmugam V. Chronic neutrophilic leukemia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/myeloproliferativeCNL.html. Accessed September 22nd, 2021.
Definition / general
  • Rare myeloproliferative neoplasm characterized by persistent peripheral blood neutrophilia, bone marrow hypercellularity and hepatosplenomegaly
  • Requires exclusion of reactive neutrophilia as well as other myeloproliferative neoplasmshronic myeloid leukemia (including typical, atypical and neutrophilic variants), polycythemia vera, essential thrombocythemia, primary myelofibrosis or myelodysplastic / myeloproliferative neoplasm
Essential features
  • Persistent blood neutrophilia (≥ 25 x 109/L); with neutrophil ≥ 80% and myeloid precursors (promyelocytes, myelocytes and metamyelocytes) comprising < 10% of the white blood cells in peripheral blood
  • Hypercellular bone marrow with predominance of neutrophilic granulocytes and blasts < 5%
  • No dysgranulopoiesis
  • CSF3R activating mutations are common
  • Lacks BCR-ABL1 gene rearrangement, which distinguishes CNL from the neutrophilic variant of chronic myeloid leukemia
  • Must be distinguished from reactive leukemoid reactions that can be seen in association with infectious or inflammatory processes or as paraneoplastic such as plasma cell neoplasms or other neoplasia
ICD coding
  • ICD-10: D47.1 - Chronic myeloproliferative disease; also applicable to myeloproliferative disease, unspecified
Epidemiology
Sites
  • Peripheral blood
  • Bone marrow
  • Spleen
  • Liver
Pathophysiology
Etiology
  • Unknown
  • Some cases are associated with cytotoxic chemotherapy (Br J Haematol 2005;128:275)
  • Substantial number of reported cases are associated with plasma cell neoplasm; these cases likely represent a neutrophilic leukemoid reaction secondary to production of G-CSF by neoplastic plasma cells (Br J Haematol 2015;171:400)
Clinical features
Diagnosis
  • World Health Organization (WHO) 2016 revised diagnostic criteria:
    1. Peripheral blood white blood cell count ≥ 25 x 109/L
      • Segmented neutrophils plus bands neutrophils constitute ≥ 80% of the white blood cells
      • Neutrophil precursors (promyelocytes, myelocytes and metamyelocytes) constitute < 10% of the white blood cells
      • Myeloblasts rarely if ever observed
      • Monocyte count < 1 x 109/L
      • No dysgranulopoiesis
    2. Hypercellular bone marrow
      • Neutrophilic granulocytes increased in percentage and number
      • Neutrophil maturation appears normal
      • Myeloblasts constitute < 5% of the nucleated cells
    3. Not meeting WHO criteria for BCR-ABL1 positive chronic myeloid leukemia, polycythemia vera, essential thrombocythemia or primary myelofibrosis
    4. No rearrangement of PDGFRA, PDGFRB or FGFR1 and no PCM1-JAK2 fusion
    5. CSF3R T618I or another activating CSF3R mutation or persistent neutrophilia (≥ 3 months), splenomegaly and no identifiable cause of reactive neutrophilia including absence of a plasma cell neoplasm or if a plasma cell neoplasm is present, demonstration of clonality of myeloid cells by cytogenetic or molecular studies (Pathology 2021;53:339)
Laboratory
  • Persistent mature neutrophilia
  • Absence of monocytosis, basophilia, eosinophilia or increased immature myeloid cells
  • Majority of patients present with mild anemia (Leukemia 2005;19:313)
  • Elevated lactate dehydrogenase (LDH) and leukocyte alkaline phosphatase (LAP)
  • Elevated vitamin B12 and uric acid
Prognostic factors
Case reports
Treatment
Microscopic (histologic) description
  • Hypercellular bone marrow with increased myeloid to erythroid ratio; up to 20:1
  • Increase in neutrophilic granulocytes
  • Myeloblasts and promyelocytes are not increased
  • No dysplasia in erythroid and myeloid series or megakaryocytes
  • Spleen with leukemic neutrophilic infiltrate in the red pulp
  • Liver with mature leukemic granulocytes in sinusoids or portal spaces
Microscopic (histologic) images

Contributed by Jingwei Li, M.D., Ph.D. and Vignesh Shanmugam, M.D.

Hypercellular bone marrow with myeloid predominance

Increased neutrophilic granulocytes

Cytology images

Contributed by Jingwei Li, M.D., Ph.D. and Vignesh Shanmugam, M.D.

Increased neutrophilic granulocytes

Toxic granulation and Döhle bodies

Peripheral smear description
  • Peripheral blood with neutrophilia, including mature neutrophils and bands
  • Toxic granulation and Döhle bodies in neutrophils
Peripheral smear images

Contributed by Jingwei Li, M.D., Ph.D., Vignesh Shanmugam, M.D. and Roberto N. Miranda, M.D.

Neutrophilic leukocytosis

Toxic granulation and Döhle bodies

Leukocytosis

Myeloid cells

Molecular / cytogenetics description
  • CSF3R mutations, up to 89% in a case series (N Engl J Med 2013;368:1781)
  • Can associate with ASXL1 or SETBP1 mutations
  • JAK2 V617F can also be observed
  • Cytogenetic studies are normal in 90% of cases
  • Remaining cases show:
    • Gains of chromosomes 8, 9 and 21
    • del(7q), del(11q), del(12p) and del(20q)
    • Nullisomy 17
  • Absence of BCR-ABL1 rearrangement
  • Absence of rearrangements in PDGFRA, PDGFRB, FGRF1 or PCM1-JAK2
Sample pathology report
  • Bone marrow core biopsy and clot specimen, aspirate smears and peripheral blood:
    • Chronic neutrophilic leukemia, 1% blasts (see comment)
    • Comment:
      • The bone marrow core biopsy is adequate in size and quality. The marrow is markedly cellular (> 95% cellular). Erythroid precursors are decreased and exhibit adequate maturation. Myeloid cells are markedly increased and exhibit maturation. Megakaryocytes are present in normal number and morphologically are unremarkable. Scattered mast cells are seen and do not form aggregates. Scattered lymphocytes and plasma cells are seen. Lymphoid aggregates are not identified. Bone trabeculae exhibit focal osteoblastic activity with no osteosclerosis.
      • Reticulin stain shows no significant reticulin fibrosis. Trichrome stain shows no abnormal collagen fibrosis.
      • Immunohistochemistry for CD34 reveals that less than 5% of marrow cells are positive. In situ hybridization for kappa and lambda immunoglobulin light chains demonstrate polytypic expression in the plasma cells.
      • Bone marrow aspirate smears show a cell differential with blasts 1%, promyelocytes 2%, myelocytes 2%, metamyelocytes 2%, and granulocytes and bands aggregate to 82%; lymphocytes 3%, plasma cells 2% and erythroid precursors 4%. The myeloid to erythroid ratio is 23 (91:4).
      • FISH assays did not show rearrangements of PDGFRA, PDGFRB, FGFR1 or BCR-ABL1.
      • Next generation sequencing showed the following findings: Pathogenic single nucleotide variants and small insertions / deletions:
          • ASXL1 NM_015338 c.1534C>T p.Q512* - in 46.6% of 1104 reads
          • CSF3R NM_156039 c.1853C>T p.T618I - in 41.2% of 699 reads
        • Read count analysis shows gain of JAK2 (on 9p).
        • FLT3 ITD is not detected.
      • Comment: The findings are of a hypercellular marrow with myeloid hyperplasia with no significant fibrosis or increase in blasts. No significant dysplasia is noted on the aspirate smear. Next generation sequencing using probes for 81 gene mutations associated with myeloid neoplasms demonstrated a canonical CSF3R (T618I) mutation along with pathogenic ASXL1 mutations. FISH analysis did not show rearrangements involving PDGFRA, PDGFRB, FGFR1 or BCR-ABL1.
      • The diagnosis of chronic neutrophilic leukemia is rendered based on the presence of persistent neutrophilia (69.78 x 109/L neutrophils, immature myeloid cells < 10%) and CSF3R mutation.
Differential diagnosis
  • Chronic myeloid leukemia (CML):
    • Associated with BCR-ABL1 fusion gene, frequent basophilia, thrombocytosis or eosinophilia
  • Neutrophilic chronic myeloid leukemia (N-CML):
    • Uncommon BCR-ABL1 fusion that results in a 230 kD fusion protein (p230)
  • Atypical CML:
    • Prominent granulocytic dysplasia and left shift
  • Chronic myelomonocytic leukemia (CMML):
    • Chronic monocytosis (> 1 x 109/L) and dysplasia
  • Leukemoid reaction / infection:
    • Rule out underlying infection or other malignancies (plasma cell neoplasms and others)
    • Lacks CSF3R mutations or other cytogenetic abnormalities seen in CNL listed above in the molecular / cytogenetics section
Board review style question #1

A 53 year old man presents with abdominal pain. Abdominal imaging shows splenomegaly and a CBC shows leukocytosis (70 x 109/L) with 95% neutrophils. A representative image of the bone marrow biopsy is shown below. An extensive laboratory work up is negative for infection or other causes that could explain these findings. Molecular studies do not reveal a BCR-ABL rearrangement. What is the gene that is most commonly mutated in this condition?

  1. CSF3R
  2. JAK2
  3. NOTCH2
  4. RUNX1
  5. TET2
Board review style answer #1
A. CSF3R, which is the gene that is most frequently mutated in chronic neutrophilic leukemia.

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Reference: Chronic neutrophilic leukemia
Board review style question #2
Which of the following features distinguishes chronic neutrophilic leukemia (CNL) from atypical chronic myeloid leukemia, BCR-ABL1 negative?

  1. Lack of basophilia in CNL
  2. Lack of dysgranulopoiesis in CNL
  3. Lack of monocytosis in CNL
  4. Presence of ASXL1 mutation in CNL
  5. WBC count > 50 x 109/L
Board review style answer #2
B. Lack of dysgranulopoiesis. Granulocytic dysplasia is not seen in chronic neutrophilic leukemia, while it is a typical feature of atypical CML.

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Reference: Chronic neutrophilic leukemia
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