The patient is a 26-year-old male who was diagnosed in CML blast crisis in November 2005. He received induction therapy followed by a peripheral stem cell transplant from a female sibling in January 2006. Chimerism studies performed in May 2007 showed 100% of cells to be XX karyotype. He remained in remission until June 2008, when chimerism studies showed 12% of his cells then to be of XY karyotype. An attempt at bone marrow aspirate was unsuccessful; however, a marrow biopsy was obtained. The marrow was 100% cellular with distinct areas of normal hematopoiesis and areas of expanded blast populations. The first image illustrates a normal hematopoietic area. Megakaryocytes are readily identified. Both erythroid and myeloid series show terminal maturation. There is no evidence of an expanded blast population.