Bone marrow neoplastic

Bone marrow - neoplastic myeloid


Juvenile myelomonocytic leukemia

Topic Completed: 1 August 2011

Minor changes: 20 January 2022

Revised: 31 December 2018, last major update August 2011

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Juvenile myelomonocytic leukemia [title] (JMML)

Nikhil Sangle, M.D.
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Cite this page: Sangle N. Juvenile myelomonocytic leukemia. website. Accessed January 28th, 2022.
Definition / general
  • JMML
  • Formerly called juvenile chronic myelogenous leukemia
  • Resembles CMML more than CML
  • 70% are children less than 3 years old, range of 1 month to teenagers
  • 10% associated with neurofibromatosis 1 and deletion of NF1 gene
  • Due to stem cell defect causing deranged hematopoiesis
  • Varied clinical presentation may include failure to thrive, malaise, fever, bleeding, pallor, lymphadenopathy and hepatosplenomegaly; less frequently skin, lung and GI involvement; rarely CNS involvement (J Pediatr Hematol Oncol 2007;29:770)
  • Most patients die of disease, although it may wax and wane
  • Diagnosis: absolute monocyte count > 1 × 109/L AND < 20% blasts + promonocytes in marrow AND no Philadelphia chromosome AND no BCR-ABL AND at least two of the following: HbF increased for age, myeloid precursors in blood smear, WBC > 10 × 109/L, clonal abnormality or GM-CSF hypersensitivity of myeloid progenitors in vitro (Leukemia 2003;17:277, Table)
  • Typically WBC is 20 - 30 × 109/L with granulocytes and monocytes, occasional dysplasia but not prominent
Case reports
Microscopic (histologic) description
  • Peripheral blood: leukocytosis with neutrophilia, monocytosis, nucleated red blood cells
  • Bone marrow: hypercellular with granulocytic hyperplasia, 5 - 30% monocytes, decreased megakaryocytes, blasts + promonocytes < 20%, dysplasia not prominent, reticulin fibrosis rare
  • Phenotyping: no specific immunophenotypic abnormality
Microscopic (histologic) images

Images hosted on PathOut server:

Peripheral blood:

Increased leukocytes, primarily monocytes
(3 at top) and neutrophils / myelocyte and
monocytes are at lower left, also 2 late
polychromatic normoblasts

Bone marrow biopsy:

Markedly cellular marrow with numerous
myelocytes, also scattered erythroid
precursors with clear cytoplasm and
round dense nuclei, megakaryocytes are reduced

Bone marrow smear:

Numerous myelocytes
and a few monocytes,
only slightly increased

4 year old child with isolated monosomy 7 of childhood, anemia, thrombocytopenia and leukocytosis:

Peripheral blood
shows mature
monocytes and

Bone marrow biopsy is markedly hypercellular
with immature neutrophils and monocytes,
scattered erythroid precursors and reduced

Bone marrow smear shows
increased monocytes, promonocytes
and large multinucleated polychromatic
erythroid precursors


Fetal hemoglobin of
peripheral blood shows
50% of cells contain
HbF (Kleihaur-Betke stain)

Positive stains
Molecular / cytogenetics description
Molecular description:
Cytogenetics description:
  • Usually normal, occasionally monosomy 7
  • NO Philadelphia chromosome or BCR-ABL
Differential diagnosis
Additional references
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