Myeloid Sarcomas

Also known as granulocytic sarcomas, chloromas, and extra-medullary myeloid tumors, myeloid sarcomas are tumors of immature myeloid precursors.10 They may precede or occur concurrently with another hemato-logic condition, such as chronic myelogenous leukemia (CML), AML, or other myeloproliferative disorders.1011 They also may be a sign of relapsed disease.12 These patients should be treated with systemic induction therapy, regardless of whether or not the bone marrow is involved. On physical examination, myeloid sarcomas frequently have a purplish hue, and may be associated with itching.12 When placed in dilute acid, myeloid sarcomas turn green, because of their increased content of myeloperoxidase.4 The diagnosis should be suspected if eosinophilic myelocytes are present in a hematoxylin— eosin-stained biopsy.4 If Auer rods are present or a myeloid origin detected, the diagnosis is con-firmed.41314 CD43 positivity in the absence of CD3 is a nonspecific but sensitive marker for myeloid sarcoma.10 Three types of myeloid sarcomas are described in the World Health Organization (WHO) classification:

(1) blastic granulocytic sarcoma, which is composed almost exclusively of myeloblasts; (2) immature form of granulocytic sarcoma, composed of a mixture of promyelocytes and myeloblasts; and (3) differentiated granulocytic sarcoma, composed of maturing neutrophils and promyelocytes.1011

Granulocytic sarcomas occur commonly in subcutaneous tissues, but can affect any organ.12 Patients presenting with an extramedullary chloroma causing spinal cord compression benefit from adequate local spine radiation (in addition to chemotherapy), and have a higher chance of neurologic recovery.5

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