blastic plasmacytoid dendritic cell neoplasm (BPDCN)

CD4+, CD56+, CD123+, CD303+

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 2016 Classification

BPDCN is now its own catergory within the WHO Classification of Myeloid Neoplasms and Acute Leukaemia

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.

———————

References:

The Haematologist 2018

Blood 2013

WHO 2016 Classification

How to treat BPDCN