Blastic plasmacytoid dendritic cell neoplasm (BPDCN)

Usually the blasts are medium sized, have irragular nuclei with fine, open chromatin and one or more nucleoli, scant faintly basophilic cytoplasm. Vacuolisation may occur. Morphologically they can not bedistinguished from other leukemias,sometimes mimicking lymphoma with small pseudo-lymphoid cells, with less blastoid chromatin or mimicking monoblastic leukemia with large, strongly basophilic cytoplasm.
Immunephentyping showing blasts positive for HLA-Dr (strong), CD4, CD56 and CD123. Other markers may be variably positive; TdT, CD2, CD7, CD33, CD36, and CD38. CD117, CD34, MPO, CD13, CD19, CD79a, CD3, CD5 and CD8 are negative.