Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive hematopoietic neoplasm of immature plasmacytoid dendritic cells. Before the cell of origin was elucidated, it was previously termed "CD4+/CD56+ hematodermic neoplasm," "agranular CD4+ natural killer (NK) cell leukemia," "blastic NK-cell lymphoma," and "blastic NK leukemia/lymphoma." While there is a high frequency of concurrent cutaneous and bone marrow involvement at presentation, some cases may present with disease localized to the skin. Since the most common site of involvement is the skin, the diagnosis is generally made via skin biopsy. However, limited experience with this rare entity may lead to diagnostic delay. The histopathologic, immunohistochemical, and molecular findings as well as the current diagnostic criteria for BPDCN are reviewed. In addition, the differential diagnosis with acute myeloid leukemia with CD4/CD56/CD123 positivity and reactive plasmacytoid dendritic cell hyperplasia is discussed.