Myeloid Sarcoma : Introduction
Myeloid sarcoma is a solid tumor consisting of extramedullary proliferation of myeloid precursors, including myeloblasts, promyelocytes, and myelocytes (as shown in this image). It has also been referred to as chloroma, granulocytic sarcoma, or extramedullary myeloid tumor. It may or may not be associated with a myeloid neoplasm in the bone marrow. Myeloid sarcoma is considered diagnostic of acute myeloid leukemia (AML) and should be classified and treated accordingly, regardless of the bone marrow or peripheral blood status. It may be the first manifestation of an acute leukemia or may signal relapse in a previously treated patient. It may also signal transformation to acute leukemia in patients with myeloproliferative disorders or myelodysplastic syndromes. In 25% of cases, it occurs in the absence of other evidence of AML and may predate it by months or years. About 35% of adults present with a concurrent myeloid disorder such as AML (most common), myelodysplastic syndrome, or myelproliferative neoplasm. In the remaining cases (about 40%), there is a prior history of a myeloid neoplasm. Myeloid sarcoma is more common in pediatric AML (seen in 10% of cases) and is often associated with t(8;21), inv(16), or 11q23 translocations.