It can also appear as a primary manifestation of relapse in a previously treated AML patient in remission.7 Additionally, in recent years, there have also been increasing reports of the development of MS following allogeneic stem cell transplantation, manifesting either as an isolated disease or along with relapse within the bone marrow.8-12 A crucial event in the pathogenesis may be the development of a novel chimeric gene and message as the result of the fusion of two genes: ETO from chromosome 8 and AML1 from chromosome 21.13 Here, RUNX1 is linked to myeloid sarcoma.