blastic plasmacytoid dendritic cell neoplasm (BPDCN)
CD4+, CD56+, CD123+, CD303+
CD3-, CD14-, CD19-, CD34-, MPO-
Intro
Dendritic cells (DC) - Antigen-presenting cells found in tissues that have contact with the external environment (e.g. skin, then called Langerhans cells)
Plasmacytoid dendritic cell (PDC) - produce large quantities of type 1 interferon (in addition to IL-2, IL-6 and TNF) in response to viral infection, resulting in T-cell activation
Blastic plasmacytoid dendritic cell (BPDC) - malignant PDC’s
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) - rare and highly agressive malignancy of PDC’s
Clinical Presentation
Median age at diagnosis - 70 y.o.
Typically skin lesions, most commonly on the head, face or upper torso
Can occur de novo or in the context of pre-existing CMML & other MPD/MDS syndromes.
Bone marrow failure
Occasionally lymphadenopathy, hepatosplenomegaly
WHO-HAEM5 Classification
BPDCN falls under the Dendritic cell and histiocytic neoplasms categories.
Aspirate Morphology
The malignant PDC’s are easily mistaken for myeloid or monocytoid lineage blasts
Classic appearance - medium sized cell with an eccentric nucleus and tail-shaped cytoplasm containing vacuoles
Immunophenotyping
Most commonly CD123+, CD4+, CD56+ (Think ‘123456’)
Also CD303 + (CD303 = antibody against blood-derived dendritic cell antigen-2 (BDCA-2))
Negative for MPO and other myeloid/monocytoid antigens
Cytogenetics / Molecular
No disease-defining abnormality yet identified
The usual culprits are often involved - TET2, ASXL1, RAS and TP53
Prognosis
Extremely poor, adult median OS 8-14 months despite intensive chemotherapy regimens
Treatment
Varying strategies have been used:
AML-like - response rate 70-80%
ALL-like - response rate 70-80%, but median OS remains 2 years
Lymphoma-like - e.g. CHOP-like chemo, response rate 30%
Overall survival remains largely the same whichever strategy used
Allogeneic HSCT if patient fit enough and achieves a CR.
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