BPDCN is a rare and aggressive malignancy of plasmacytoid dendritic cell precursors that represents 0.44% of all hematological cancers [1, 2]. Previously classified as a subtype of acute myeloid leukemia (AML), the 2016 World Health Organization (WHO) Classification redefined BPDCN as a unique entity separate from AML [3]. BPDCN commonly involves the skin and bone marrow, with less frequent involvement of lymph nodes and visceral organs [4]. Although true incidence is unknown, central nervous system (CNS) involvement of BPDCN has been estimated to occur in as many as 20À60% of patients [5-8]. Historically, CNS staging and prophylaxis practices have been variable and until recently were not required during enrollment for clinical trials. A recent survey of 39 centers conducted by Valentini et al., found 30% of those surveyed didnLt include CSF exam at diagnosis [8]. Martin-Martin et al., found that CNS involvement occurred in 60% of patients at diagnosis, in up to 30% at relapse, and suggested the CNS may act as a sanctuary site for BPDCN [6].

Until 2018, there were no FDA approved therapies for BPDCN and patients were often treated with conventional AML, acute lymphoblastic leukemia (ALL), or lymphoma type chemotherapy regimens [7]. Patients achieving complete responses (CR) with frontline therapy are often considered for allogeneic hematopoietic stem cell transplant (HSCT), but despite these treatments often relapse with median overall survival remaining between 8 and 24 months [1, 9].