Paediatric blastic plasmacytoid dendritic cell neoplasm: a single-centre case series of 18 children and review of the literature.

The incidence of paediatric blastic plasmacytoid dendritic cell neoplasm (BPDCN) is extremely low, and little is known about the disease. This study aims to investigate its clinical course and optimal management. We retrospectively analysed the clinical manifestations, laboratory findings, treatment responses, and survival outcomes of 18 paediatric patients with BPDCN treated at our hospital. In this cohort, the male-to-female ratio was 2.6, and the median age of onset was 12 years. Bone marrow involvement was observed in 88.9% of patients (16/18), making it the most commonly affected site, followed by the skin (13/18) and lymph nodes (13/18). Central nervous system infiltration occurred in the youngest patient (Case 13), who experienced relapse after matched sibling donor haematopoietic stem cell transplantation (MSD-HSCT). Immunohistochemical and flow cytometry analyses revealed a distinct immunophenotype, with high expression of CD4 (94.4%), CD56 (100%), CD123 (100%), CD304 (100%), and HLA-DR (100%), and no expression of myeloperoxidase and CD19. In terms of the initial response, 14 patients received acute lymphoblastic leukaemia (ALL)-like regimens, all of whom achieved complete remission (CR) after induction chemotherapy. All 18 patients proceeded to HSCT post-chemotherapy, including 15 haploidentical and 3 MSD transplants. The 4-year overall survival (OS) and event-free survival (EFS) rates for the entire cohort were 94.4% ± 5.4% (95% CI, 83.8%-100.0%) and 87.7% ± 8.2% (95% CI, 71.6%-100.0%), respectively. Paediatric patients with BPDCN who receive allogeneic HSCT-particularly haploidentical HSCT-during CR following ALL-like induction chemotherapy appear to have favorable outcomes in this limited cohort.