- 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
- 27 year old woman with punched out, lytic, intramedullary lesion in fibula (Case of the Week #130)
- Aggressive treatment recommended (Leukemia 2007;21:340, Cancer 2002;94:1739)
- Usually evolves to AML or has additional tumor masses at other sites
Bone tumor
- 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)
Lymph node:
Cells have fine chromatin
resembling lymphoblastic
lymphoma
Large blast cells resemble large
cell lymphoma, also some
eosinophilic myelocytes
Tumor cells have irregularly
folded and convoluted nuclei
Resembles lymphoblastic lymphoma,
but has cytoplasmic granules
and distinct nuclei
Many tumor cells have
azurophilic granules
Tumor cells mix with residual
normal lymphocytes
Immature cells with moderate to
abundant cytoplasm, round / oval
nuclei, distinct and prominent nucleoli
and immature eosinophils
Lymph node has prominent
eosinophilic myelocytes and blasts
Case of the week #130 (bone):
CD45 / LCA
CD45RO
CD3
CD34
CD20
Other:
Has blasts with numerous
azurophilic granules and
promyelocytes, classified as
AML with maturation
Skin eosinophilic
myelocytes and blasts
Orbital mass with t(8;21)
has blasts with
immature eosinophils
Spinal dura - some
tumor cells have
cytoplasmic granules
Stains:
Myeloperoxidase: Lymph node
Mediastinum
Chloroacetate esterase - lymph node
Lysozyme - orbit
Images hosted on other servers:
Other:
Anorectal ulcer
Stains:
Skin: various stains
Uterus
- Usually background lymphoglandular bodies
- Auer rods and eosinophilic myelocytes are rare
- Resembles large cell lymphoma (Cancer 2000;90:364)
Breast: has blasts with numerous
azurophilic granules and promyelocytes,
classified as AML with maturation
- Almost all tumors: lysozyme and CD43
- Myeloid tumors: myeloperoxidase and CD117
- Myeloblasts: CD13, CD33 (Arch Pathol Lab Med 2001;125:1448)
- Monocytic tumors: CD68 and variable CD163 (Am J Clin Pathol 2004;122:794)
- Monoblasts: CD11c (Diagn Pathol 2007;2:42), CD14, CD56 (Am J Clin Pathol 2000;114:807), CD99 (55%, Mod Pathol 2000;13:452), HLA-DR and chloroacetate esterase (Ann Saudi Med 2001;21:287)
- Other: CD4, CD34 and TdT
- 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%)
- Burkitt lymphoma
- Poorly differentiated lymphoma
- Small round cell tumors
