Blastic plasmacytoid dendritic cell neoplasm: A clinicopathologic review

• Blastic plasmacytoid dendritic cell neoplasm is a rare entity grouped with the acute myeloid leukemia-related precursor neoplasms in the 2008 World Health Organization classification. It was previously postulated to originate from natural killer cells, T cells, or monocytes but is now believed to arise from the plasmacytoid dendritic cell. The pathogenesis of blastic plasmacytoid dendritic cell neoplasm is not well understood, although the neoplasm demonstrates frequent deletion of tumor suppressor genes, including RB1, CDKN1B, CDKN2A, and TP53. Blastic plasmacytoid dendritic cell neoplasm is a clinically aggressive tumor that often initially presents as cutaneous lesions and subsequently progresses to bone marrow involvement and leukemic dissemination. It is characterized by enhanced expression of CD56, CD4, and CD123, which can be detected by flow cytometry/immunohistochemistry. The differential diagnoses include myeloid sarcoma/acute myeloid leukemia, T-cell lymphoblastic leukemia/lymphoma, NK-cell lymphoma/leukemia, and some mature T-cell lymphomas/leukemias. Patients usually respond to initial chemotherapy but often relapse. Stem cell transplant may improve survival.