Graft-Versus-Tumour Effect Following Allogeneic Haematopoietic Stem Cell Transplantation in a Paediatric Patient With Mogamulizumab-Treated Primary Cutaneous Peripheral T-Cell Lymphoma.

INTRODUCTION

Primary cutaneous peripheral T-cell lymphoma, not otherwise specified (pcPTCL-NOS), is exceptionally rare in children, and evidence guiding diagnosis and treatment is limited.

CASE PRESENTATION: A 10-year-old boy with pcPTCL-NOS refractory to chemotherapy received mogamulizumab prior to allogeneic haematopoietic stem cell transplantation (allo-HSCT). Despite a 60-day washout period, he developed prolonged steroid-refractory acute graft-versus-host disease requiring ruxolitinib and extracorporeal photopheresis. Concurrently, transient skin lesions developed at previous lymphoma sites and regressed spontaneously, with biopsy supporting the interpretation of visible graft-versus-lymphoma.

CONCLUSION

This case underscores the need to optimise allo-HSCT timing after mogamulizumab and preserve graft-versus-lymphoma effect while limiting graft-versus-host disease. Trial Registration: The authors have confirmed clinical trial registration is not needed for this submission.