Durable Remission of Chemotherapy-Refractory Myeloid Sarcoma by Azacitidine

Myeloid sarcoma is a rare disease entity of extramedullary myeloid neoplasm that can occur both as an initial isolated myeloid sarcoma without leukemic cell invasion in the peripheral blood and bone marrow, and as the secondary lesion of acute and chronic myeloid leukemias, myelodysplastic syndrome and chronic myeloproliferative neoplasms. Due to its rarity and its frequent emergence as the recurrent lesion after intensive systemic therapy, including allogeneic hematopoietic stem cell transplantation, the standard treatment has not been established for myeloid sarcoma. In this report, we presented an 84-year-old female patient with isolated myeloid sarcoma which progressed to myelodysplastic syndrome and systemic myeloid sarcoma despite various types of conventional anti-leukemic chemotherapies. However, the patient got a durable partial response by the monotherapy of azacitidine, a hypomethylating agent. She received thirteen courses of azacitidine therapy without progression. We discuss the possibility that hypomethylating agents are the novel effective and feasible therapeutic options for myeloid sarcoma, even in cases refractory to or relapsed after intensive systemic treatment. We also discuss the possible future development of hypomethylating agent-containing combinatory therapeutic strategy for myeloid sarcoma, given its direct anti-leukemic effect and immunomodulatory effect.

Somatic ASXL1 p.R693X mutation identified by next generation sequencing in isolated myeloid sarcoma involving the mediastinum

Introduction: Isolated myeloid sarcoma (MS) is characterized by extramedullary immature myeloid cell infiltration without bone marrow involvement. The diagnosis of isolated MS is sometimes difficult in cases without expression of typical immunohistochemical markers, such as CD64, MPO or lysozyme.Clinical presentation: We report a case of isolated MS involving the mediastinum, with negative staining of MPO and lysozyme, which was misdiagnosed for 20 months. A comprehensive analysis in our institution showed MS with a characteristic staining pattern positive for CD34, CD117 and CD33, but negative for MPO, lysozyme, CD3 and CD79a. Next-generation sequencing (NGS) targeting 112 acute myeloid leukemia (AML)- and myelodysplastic syndromes (MDS)-associated genes confirmed the existence of an ASXL1 p.R693X mutation with a frequency of 13.17% of total cells. The patient acquired sustainable remission under the alternative treatment of intermediate-dose cytarabine and decitabine.Discussion and conclusion: The ASXL1 p.R693X mutation, a truncated mutation, has been widely reported to be associated with poor prognosis in myeloid malignance. We report the role of this mutation and recommend the utilization of NGS to discover more profound pathobiological information with limited samples, facilitate the diagnosis, and further clarify the uncertainties of prognosis and treatment in more isolated MS patients.

Isolated Pancreatic Myeloid Sarcoma Associated with t(8;21)/RUNX1-RUNX1T1 Rearrangement

No valid treatment for isolated myeloid sarcoma (IMS) has yet been established, and no thorough genetic examinations have been performed because of its low incidence and unique manner of development. We herein report a 34-year-old man with pancreatic IMS with t(8;21)/RUNX1-RUNX1T1 rearrangement. He was treated with high-dose cytarabine followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT). This is the first report of pancreatic IMS with t(8;21). Positron emission tomography/computed tomography and genetic study are useful for the diagnosis, and allo-HSCT achieved complete remission in this patient.