Blastic plasmacytoid dendritic cell neoplasm : report of two cases.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive tumor derived from the precursor of plasmacytoid dendritic cells. We describe two cases of BPDCN. In case 1, the patient presented with multiple erythema on the trunk and arms. Histopathology of a skin biopsy specimen and immunohistochemistry demonstrated that the tumor cells were small to medium-sized with a blastoid morphology and positive for CD4, CD56, CD123 and T-cell leukemia-1 (TCL-1). In case 2, the patient presented with a solitary skin nodule and rapidly developed involvement of the bone marrow and peripheral blood. Although immunohistochemistry of the infiltrating tumor cells demonstrated positivity for CD4, CD56, CD123 and TCL-1, the cells were large with a distinct nucleolus, and different from those of typical BPDCN. The atypical morphological features of BPDCN may be diagnostically problematic, and should therefore be recognized correctly.