[A case of myeloid sarcoma diagnosed by FISH]

Myeloid sarcoma (MS) is a tumor mass of myeloblasts or immature myeloid cells occurring in an extramedullary site or in bone. The tumor mass may precede or occur concurrently with acute or chronic myeloid leukemia or with other types of myeloproliferative disorders or myelodysplastic syndromes. MS is a rare disease, estimated to comprise between 2 to approximately 14% of acute myeloid leukemia. On the other hand, 95% of cases of CML have characteristic t (9;22) cytogenetic abnormality and BCR/ABL fusion gene at diagnosis. We here report the clinical significance of FISH in a diagnosis of MS that formed tumor in femur during the chronic phase of CML.