Title: allogeneic peripheral blood stem cell transplantation for Myeloid sarcoma: a single-center experience

Myeloid sarcoma (MS) is a rare extramedullary manifestation of myeloid neoplasms and usually has poorer outcomes than acute myeloid leukemia without extramedullary disease. Allogeneic hematopoietic stem cell transplantation is the most effective consolidation, but evidence on allogeneic peripheral blood stem cell transplantation (allo-PBSCT), especially from haploidentical donors, is limited.

We retrospectively reviewed 20 consecutive patients with biopsy-confirmed MS who underwent allo-PBSCT at our center (2012-2025). All grafts were peripheral blood. Donors were haploidentical in 14 patients (70.0%), matched related in 4 (20.0%), and matched unrelated in 2 (10.0%). Overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan - Meier method; relapse incidence (RI), non-relapse mortality (NRM), and graft-versus-host disease (GVHD) were analyzed as competing risks.

Twenty patients (median age, 28.5 years) were included; 45.0% had isolated extramedullary MS and 55.0% had concurrent bone marrow disease. At transplantation, 16 (80.0%) were in first complete remission, 18 (90.0%) were measurable residual disease (MRD) negative, and all had HCT-CI = 0. After a median follow-up of 38 months, 1- and 2-year OS and DFS were both 90.0%, with RI 0% and NRM 10.0%; at 3 years, OS/DFS were 81.8%, RI 8.2%, and NRM 10.0%. Haploidentical recipients (14/20) had comparable outcomes (3-year OS/DFS 92.9%, no relapse, NRM 7.1%). Acute GVHD occurred in 60.0%, but grade II - IV in only 20.0%; chronic GVHD was 30.0%, mostly mild.

Allo-PBSCT can achieve durable remission in selected MS patients and is a practical option when an HLA-matched donor is unavailable.