Leukemia acute
AML not otherwise categorized
Myeloid sarcoma



Topic Completed: 1 March 2013

Revised: 21 November 2019

Copyright: (c) 2001-2019, PathologyOutlines.com, Inc.

PubMed Search: Myeloid sarcoma [title]

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Cite this page: Mihova D. Myeloid sarcoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/leukemiagranulocytic.html. Accessed December 13th, 2019.
Definition / general
  • Extramedullary tumor mass of neoplastic immature myeloid (granulocytic or monocytic) cells
  • Also called extramedullary myeloid tumor, granulocytic sarcoma, chloroma
  • See also descriptions in various chapters
  • Often misdiagnosed, particularly without immunostains
  • Present in 2 - 8% of AML patients; prognosis is that of underlying leukemia
  • Equivalent to blast transformation in setting of myelodysplastic syndrome or myeloproliferative disease (Korean J Lab Med 2006;26:143)
  • Usually associated with AML M4 or M5 (M4e or M5a in children), CML, chronic idiopathic myelofibrosis, hypereosinophilic syndrome or polycythemia vera
  • Rarely no leukemia / myelodysplasia is identified in blood or bone marrow (J Neurosurg 2006;105:916)
  • Common sites: lymph nodes, subperiosteal bone, skin, orbit, spinal canal and mediastinum
Case reports
Treatment
Gross images
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Bone tumor

Microscopic (histologic) description
  • Blastic type: myeloblasts with mild / moderate rim of basophilic cytoplasm, fine nuclear chromatin, 2 - 4 nucleoli
  • Immature type: myeloblasts, promyelocytes, eosinophilic myelocytes
  • Differentiated type: promyelocytes, eosinophilic myelocytes and more mature forms; rarely crystalline inclusions similar to Charcot-Leyden crystals (Arch Pathol Lab Med 2002;126:85)
Microscopic (histologic) images

Lymph node:
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Cells have fine chromatin
resembling lymphoblastic
lymphoma

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Large blast cells resemble large
cell lymphoma, also some
eosinophilic myelocytes

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Tumor cells have irregularly 
folded and convoluted nuclei

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Resembles lymphoblastic lymphoma,
but has cytoplasmic granules
and distinct nuclei


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Many tumor cells have
azurophilic granules

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Tumor cells mix with residual
normal lymphocytes

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Immature cells with moderate to
abundant cytoplasm, round / oval
nuclei, distinct and prominent nucleoli
and immature eosinophils

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Lymph node has prominent
eosinophilic myelocytes and blasts



Case of the week #130 (bone):

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CD45 / LCA

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CD45RO

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CD3

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CD34

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CD20



Other:
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Has blasts with numerous
azurophilic granules and
promyelocytes, classified as
AML with maturation

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Skin eosinophilic
myelocytes and blasts

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Orbital mass with t(8;21)
has blasts with
immature eosinophils

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Spinal dura - some
tumor cells have
cytoplasmic granules



Stains:
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Myeloperoxidase: Lymph node

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Mediastinum

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Chloroacetate esterase - lymph node

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Lysozyme - orbit



Images hosted on other servers:

Other:
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Anorectal ulcer

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Appendix

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Breast


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Bladder

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Small intestine

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Testes



Stains:
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Breast (left), CD43 (right)

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Skin: various stains

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Uterus

Cytology description
  • Usually background lymphoglandular bodies
  • Auer rods and eosinophilic myelocytes are rare
  • Resembles large cell lymphoma (Cancer 2000;90:364)
Cytology images
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Breast: has blasts with numerous
azurophilic granules and promyelocytes,
classified as AML with maturation

Positive stains
Negative stains
Molecular / cytogenetics description
  • Most common are monosomy 7 (11%), trisomy 8 (10%) and MLL rearrangements (9%)
  • Also inv(16), trisomy 4, monosomy 16, 16q-, 5q-, 20q-, trisomy 11, t(8;21)(q22;q22) in pediatric cases and NPM1 mutations (16%)
Differential diagnosis
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