Lymphadenopathy in a 3-Year-Old Boy 17 Months After Bone Marrow Transplantation for Acute Myeloid Leukemia (AML-M5a)

Archives of Pathology & Laboratory Medicine, Jul 2005 by Turyan, Hach V, Bourgeois, Danyel, Lazarchick, John

Immunohistochemical stains are essential to confirm the diagnosis of myeloid sarcoma.5 Myeloperoxidase and chloroacetate esterase are often positive in the myeloblastic variant, while lysozyme and CD68 positivity can be seen in the rarer monoblastic variant. Paradoxically, most myeloid sarcomas will demonstrate positive staining with CD43, a T-cell marker.6 Other B- and T-cell markers are characteristically negative, including CD79a, CD20, CDS, and CD30. CD45 is often also positive, but may show only weak staining. The myeloid sarcoma in this case stained positive only with CD68 (focally) and CD43 (diffusely) and was negative for myeloperoxidase, chloroacetate esterase, B- and other T-cell markers. The lysozyme stain was not performed.

The differential diagnosis of myeloid sarcoma includes, but is not limited to, non-Hodgkin lymphoma (precursor B- and T-cell, Burkitt lymphoma, large B-cell lymphoma), small round cell tumors of childhood (neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, primitive neuroectodermal tumor, and medulloblastoma), carcinoma, and melanoma. Myeloid sarcoma is often misdiagnosed, most commonly as non-Hodgkin lymphoma, and especially in patients without a prior history of myeloid malignancy.7 A high index of suspicion is therefore necessary to avoid misdiagnosis, especially in poorly differentiated tumors of unknown origin.

The prognosis of patients with AML and myeloid sarcoma is generally considered to be less favorable than that of patients with AML alone. However, a more favorable prognosis is associated with the t(8;21).8 Patients are routinely treated with high-dose chemotherapy, with or without radiotherapy, but as many as 85% relapse within 1 year. Most cases of myeloid sarcoma that occur in patients without a previous diagnosis of leukemia will progress to AML within 1 year.9 In patients with isolated myeloid sarcoma without progression to leukemic disease, treatment with corticosteroids, chemotherapy, and radiotherapy may be curative and will prolong survival.1,10

References

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2. Fletcher CDM. Diagnostic Histopathology of Tumors. VoI 2, 2nd ed. New York, NY: Churchill Livingstone; 2000:1204-1205.

3. Bird JC, Edenfield WJ, Shields DJ, Dawson NA. Extramedullary myeloid cell tumors in acute nonlymphocytic leukemia: a clinical review, j CHn Oncol. 1995; 13:1800-1816.

4. King A. A case of chloroma. Monthly J Med. 1853;17:97.

5. Chang CC, Eshoa C, Kampalath B, Shidman VB, Perkins S. lmmunophenotypic profile of myeloid cells in granulocytic sarcoma by immunohistochemistry: correlation with blast differentiation in bone marrows. Am J CUn Pathol. 2000; 114:807-811.

6. Segal GH, Stoler MH, Tubbs RR. The "CD43" only phenotype: an aberrant, non-specific immunophenotype requiring comprehensive analysis for lineage resolution. AmJ Clin Pathol. 1992;97:861-865.