Blastic plasmacytoid dendritic neoplasm (BPDN) or BPDN-like lesion presenting after influenza vaccination and resolving with topical high potency steroid

BPDN: Blastic plasmacytoid dendritic cell neoplasm HSCT: Hematopoietic stem cell transplantation INTRODUCTION Blastic plasmacytoid dendritic cell neoplasms (BPDN) are exceeding rare T-cell neoplasms that carry a dismal prognosis. Today, the exact etiology of the disease is unclear, and to our knowledge, no cases of BPDN have been reported at the site of vaccination injection. Additionally, all currently described cases described have dismal prognosis, and, to our knowledge, there are no reports of such lesions responding to topical steroid treatment. Herein, we present an unusual case of BPDN occurring at an influenza vaccination site that subsequently resolved after high-potency topical steroid treatment.