Hematopoietic stem cell transplantation for rare hematological malignancies

Hematopoietic stem cell transplant can be curative for hematologic malignancies. In this chapter, we review and summarize the available data on selected rare lymphoid and myeloid malignancies. Allogenic hematopoietic stem cell transplant (Allo-HSCT) can induce durable remission in patients with advanced systemic mastocytosis. Adequate debulking before transplantation improves the outcomes. Myeloablative conditioning (MAC) may be associated with better survival. Allo-HSCT is recommended early in the disease course for refractory multisystem Langerhans cell histiocytosis (MS-LCH) in patients who have available donors. MAC is preferred because of lower relapse rate. Auto-HSCT may be performed in selected patients with no donors. For chronic myelomonocytic leukemia (CMML), patients with lower CMML-specific prognostic scoring system score and higher Karnofsky performance status should be referred early for allo-HSCT evaluation. Allo-HSCT should be considered in suitable platelet-derived growth factor receptor A/B rearrangement-negative patients with hypereosinophilic syndrome who have early signs of organ damage and have failed standard therapy. Upfront auto-HSCT consolidation is beneficial for high-risk primary central nervous system lymphoma (PCNSL) patients. High-dose immune chemotherapy with auto-HSCT carries a low treatment-related mortality and is offered as frontline therapy to eligible patients with chemosensitive PCNSL. Allo-HSCT extends long-term survival in patients with aggressive adult T-cell leukemia/lymphoma. Auto-HSCT is considered for patients with extra-nodal natural killer (NK)/T cell lymphoma with advanced-stage disease in complete remission after chemotherapy. Auto-HSCT has no role in refractory nasal-type extra-nodal NK/T-cell lymphoma or ANKL, and allo-HSCT should be considered. For patients with advanced mycosis fungoides and Sezary syndrome, allo-HSCT should be recommended.