OBJECTIVETo explore the clinicopathologic features, differential diagnosis and therapy of myeloid sarcoma.

METHODSThe clinical data including clinical manifestations, laboratorial tests, histopathologicical examination, immunohistochemistry and clinical prognosis of 10 patients with myeloid sarcoma were analyzed retrospectively. Among 10 patients, 5 male and 5 female, aged 23 to 71 years old (median = 36 years).

RESULTS2 cases of myeloid sarcoma were secondary from chronic myeloid leukemia, and 1 cases of myeloid sarcoma occurred after the allogeneic hematopoietic stem cell transplantation due to acute myeloid leukemia, and the others lacked the anamnesis of malignancies. The neoplasms occurred at bone, brain, skin, breast, epididymis, uterine cervix, small intestine, ovary and lymph nodes. Microscopically, the tumor cells were round or oval, which infiltrated diffusely or arranged in single-file. The cytoplasm was scarce and immature eosinophils were scattered. The nuclei were round, oval or focally irregular, and the mitosis was visible. The neoplasms were positive for MPO, CD34, CD43, CD45, CD99 and CD117 by immunohistochemical staining. 4 patients progressed into acute myeloid leukemia from 2 to 10 months after the diagnosis of myeloid sarcoma. All of them achieved complete remission after inductive chemotherapy, but 3 patients relapsed from 3 to 12 months after remission and only survived for 14 to 23 months. 4 patients were treated by using chemotherapy before bone marrow abnormality, and with the disease-free survival for 1 to 48 months.

CONCLUSIONMyeloid sarcoma needs to be distinguished from lymphoblastic lymphoma, Burkitt's lymphoma, blastic plasmacytoid dendritic cell neoplasms and so on. The diagnosis and differential diagnosis of myeloid sarcoma are dependent on the pathological and immunohisto-chemical features. The chemotherapy and allogeneic hematopoietic stem cell transplantation of acute myeloid leukemia are the main methods for treatment of myeloid sarcoma.