General
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• Also called granulocytic / myeloid sarcoma or chloroma when it forms a mass
• See also Leukemia chapter
• Diagnosis requires a high degree of suspicion; thin sections are needed to see cytoplasmic granules
• Lymphadenopathy may be initial presentation, preceding marrow involvement by months or years
• May present with nodal infarction (Am J Surg Pathol 1989;13:177)

Case reports
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• 43 year old woman with chronic myelofibrosis progressing to AML-M7 (Eur J Haematol 2001;67:194)

Gross description
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• May have green hue (“chloroma”) due to myeloperoxidase, which fades on exposure to air

Gross images
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Retroperitoneal lymphadenopathy

Subcutaneous tumor

Granulocytic sarcoma - contributed by Dr. Mark R. Wick

Micro description
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• Cortical or sinusoidal expansion by atypical cells with preservation of follicular centers
• Blasts are large to medium size with distinct cytoplasmic borders and fine cytoplasmic granules
• Nuclei have round, folded or lobated nuclei, fine and dispersed chromatin and small to prominent nucleoli
• Often infiltrate in a single file pattern due to tumor cells insinuating between collagen fibers
• Often associated with eosinophilic myelocytes
• Auer rods may be present (Giemsa stain)
• Variable mitotic figures
• May have associated prominent sclerosis

Micro images
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Granulocytic sarcoma

Acute myeloid leukemia

Involving liver

With interspersed eosinophilic myelocytes

Cytology description
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• Cytoplasmic granules in many cells

Cytology images
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Cytologic spectrum

Virtual slides
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AML (without maturation)

Positive stains
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• Myeloperoxidase, lysozyme, chloroacetate esterase (depends on AML subtype), CD43, CD99, CD117

Electron microscopy description
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• Large electron-dense primary cytoplasmic granules and less dense secondary granules
• May have ellipsoidal crystalloid granules

Differential diagnosis
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• Ewing sarcoma
• Langerhans cell histiocytosis
• Lymphoma

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