Hematologic neoplasms
Myeloid sarcoma

Author: Sheren Younes, M.D. (see Authors page)

Revised: 20 July 2018, last major update February 2014

Copyright: (c) 2003-2018,, Inc.

PubMed search: myeloid sarcoma [title] bone

Cite this page: Younes, S. Myeloid sarcoma. website. Accessed December 12th, 2018.
Definition / general
  • Defined by WHO as a tumor mass consisting of myeloid blasts, with or without maturation, occurring at extramedullary sites
  • Leukemic infiltration is considered myeloid sarcoma ONLY if it forms a mass that effaces tissue architecture
  • Myeloid sarcoma is diagnostic of AML, regardless of bone marrow or peripheral blood involvement
  • Myeloid sarcoma occurs in 3 clinical settings:
    • Most often with concurrent AML, diagnosed by bone marrow biopsy or peripheral blood
    • History of AML, as a sign of relapse
    • As initial presentation of AML
  • May represent progression from MDS or MDS / MPD to a "blastic phase" of leukemia
  • Synonyms: chloroma, extramedullary myeloid tumor, granulocytic sarcoma
  • Bones affected are skull, paranasal sinuses, sternum, ribs, vertebrae, pelvis
Clinical features
  • Mass affecting bone, in patient with AML, history of AML, or primary
  • Clinical picture
  • Radiology
  • Biopsy, immunohistochemistry, flow cytometry
  • FISH, molecular analysis
  • Bone marrow biopsy and peripheral blood smear
  • Note: 75% misdiagnosis, commonly misdiagnosed as large cell lymphoma (Cancer 1986;58:2697)
Radiology description
Prognostic factors
  • Not well studied
  • Not influenced by age, gender, anatomical site
  • Bone marrow transplantation associated with higher probability of survival and even cure
  • Patients with isolated tumor and chromosome 7 abnormalities have worse prognosis (Leukemia 2003;17:1100)
Case reports
Clinical images

Images hosted on PathOut server:

Femur Xray, by Dr. Mark R. Wick

Case of the Week #321:

Bone scintigraphy


Gross description
  • Called "chloroma" due to peculiar green color, caused by myeloperoxidase, fades in a few hours
  • Firm with fish flesh appearance
  • May show hemorrhage and necrosis
Gross images

Images hosted on PathOut server:

Bone tumor

Microscopic (histologic) description
  • Diffuse monotonous infiltrate that destroys underlying normal structures
  • Cytologically variable
  • Three variants, according to WHO
    • Myeloid tumors: blastic type has myeloblasts with mild / moderate rim of basophilic cytoplasm, fine nuclear chromatin, 2 - 4 nucleoli
    • Immature type has myeloblasts, promyelocytes and eosinophilic myelocytes
    • Differentiated type has promyelocytes, eosinophilic myelocytes and more mature forms; rarely crystalline inclusions similar to Charcot-Leyden crystals (Arch Pathol Lab Med 2002;126:85)
  • Less common variants:
    • Monoblastic sarcoma, composed of monoblasts and associated with acute monoblastic leukemia
    • Monocytic variant, myelomonocytic variant, variant with intracytoplasmic Auer bodies
Microscopic (histologic) images
Scroll to see all images.

Images hosted on PathOut server:

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


Chloroacetate esterase - lymph node

Lysozyme - orbit


Lymph node


Case of Week #130 (bone):

Various images

Case of Week #321:

Various images







Images hosted on other servers:


Other bone


CD68 spine (left), uterus (right)


Breast (left), CD43 (right)

Cytology description
  • The blastic immature types have features of small or intermediate size lymphoma with a single cell pattern, high N / C ratio, and minimal cytoplasm.
  • The more differentiated forms show a spectrum of myeloid differentiation with granulated promyelocytes, metamyelocytes or band forms seen.
  • Resembles large cell lymphoma (Cancer 2000;90:364)
Positive stains
Negative stains
Flow cytometry description
  • Helpful for blast identification and lineage assignment
Molecular / cytogenetics description
  • 55% of patients show chromosomal aberrations as trisomy 8, monosomy 7, MLL rearrangement, inv 16, trisomy 4, monosomy 16
  • 16% show evidence of NPM mutation, shown also by cytoplasmic NPM expression
  • t(8;21) is common in pediatric patients than in adults
Differential diagnosis