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Table of Contents
Definition / general | Terminology | Epidemiology | Sites | Clinical features | Diagnosis | Radiology description | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Flow cytometry description | Molecular / cytogenetics description | Differential diagnosisCite this page: Myeloid sarcoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bonemyeloidsarcoma.html. Accessed July 14th, 2017.
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
Terminology
- Synonyms: chloroma, extramedullary myeloid tumor, granulocytic sarcoma
Epidemiology
- Any age, but median age 56 years
- Can involve many sites including bone (Am J Clin Pathol 2009;132:426)
Sites
- Bones affected are skull, paranasal sinuses, sternum, ribs, vertebrae, pelvis
Clinical features
- Mass affecting bone, in patient with AML, history of AML, or primary
Diagnosis
- 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
- CT and MRI show solid masses with variable enhancement, lytic destruction; may have soft tissue component (AJR Am J Roentgenol 2001;176:1427, AJR Am J Roentgenol 2012;199:1193)
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
- 14 year old boy with mass in the L5 vertebral body (Case of the Week #321)
- 27 year old woman with painful swelling in fibula (Case of the Week #130)
- 34 year old woman with isolated spinal granulocytic sarcoma (Oncol Lett 2013;5:1229)
- 64 year old man with isolated myeloid sarcoma (Eur J Haematol 2014;92:537)
- Temporal bone myeloid sarcoma (Clin Exp Otorhinolaryngol 2009;2:198)
- Philadelphia chromosome-positive myeloid sarcoma of bone (Ann Hematol 2013;92:1287)
Treatment
- Chemotherapy similar to AML
- Aggressive treatment recommended (Leukemia 2007;21:340, Cancer 2002;94:1739), usually evolves to AML or has additional tumor masses at other sites
- Local control by radiotherapy (Radiat Oncol 2013;8:245) and surgery
- Bone marrow transplantation
- Targeted therapy (Ther Adv Hematol 2011;2:309)
Clinical images
Images hosted on PathOut server:
Case of the Week #321:
Femur Xray, by Dr. Mark R. Wick
Case of the Week #321:
Bone scintigraphy
MRI
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
eosinophils
Stains:
Myeloperoxidase:
Case of Week #130 (bone):
Case of Week #321:
Images hosted on other servers:
Differentiated
vs. blastic
site unknown
Stains:
Myeloperoxidase:
Images hosted on PathOut server:
t(8;21) has blasts
with immature
eosinophils
Stains:
Chloroacetate esterase - lymph node
Lysozyme - orbit
Myeloperoxidase:
Lymph node
Mediastinum
Case of Week #130 (bone):
Various images
Case of Week #321:
Various images
CD99
MyoD1
NSE
PAS
Vimentin
Desmin
Images hosted on other servers:
Femur
Other bone
vs. blastic
site unknown
Various images
Stains:
CD68 spine (left), uterus (right)
Myeloperoxidase:
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
- Myeloperoxidase: sensitive and specific (Mod Pathol 1991;4:733)
- C-kit: diagnostic, may guide treatment (Arch Pathol Lab Med 2001;125:1448)
- CD68: KP1 antibody more sensitive than myeloperoxidase (Am J Clin Pathol 2000;114:807)
- CD34: positive in some types (J Clin Pathol 1999;52:705)
- Monoblasts: CD14, CD11c (Diagn Pathol 2007;2:42), CD56 (Am J Clin Pathol 2000;114:807) HLA-DR, CD99 (55%, Mod Pathol 2000;13:452), chloroacetate esterase (Ann Saudi Med 2001;21:287)
- CD15: often positive but nonspecific (Am J Surg Pathol 1993;17:1011)
- Monocytic tumors: CD68 and variable CD163 (Am J Clin Pathol 2004;122:794)
- Myeloblasts: CD13, CD33 (Arch Pathol Lab Med 2001;125:1448)
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
- Burkitt lymphoma
- Carcinoma and melanoma: different clinical history, immunohistochemistry
- Diffuse large B cell lymphoma
- Plasmacytoma
- Small round cell tumors of bone
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