Blastic plasmacytoid dendritic cell neoplasm is a rare, aggressive tumor characterized by skin and/or marrow infiltration by CD4(+) CD56(+) cells. Historically, the tumor was variably thought to arise from either monocytes, T cells or NK cells giving rise to terms such as CD4(+)/CD56(+) acute monoblastic leukemia, primary cutaneous CD4(+)/CD56(+) hematodermic tumor and blastic NK-cell lymphoma. Whilst considerable progress has been made in understanding the histogenesis, the best modality of treatment remains to be defined. We are therefore reporting this case which was successfully treated with a T-deplete allogeneic transplant and the patient is currently alive and in remission 4 years post transplant.