Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Related Cases: HP-303

The Key Features

  • Diffuse sheets of growth with minimal reactive cells

  • Tumor cells: medium sized, high N/C ratio, irregular nuclei, fine chromatin and inconspicuous nucleoli

  • CD4+, CD56+, CD123+; also CD2+, CD7+, CD43+, CD117+, and CD303+

  • CD3-, EBER-

  Clinical Futures

  • AKA: blastic NK-cell lymphoma, CD4+CD56+ hematodermic neoplasm
  • Rare, 0.27% of cases presenting as non-Hodgkin lymphoma and 0.76% of cases presenting as AML
  • Mainly involves skin (~100%), with subsequent or simultaneous dissemination to blood, lymph node and marrow
  • Not associated with EBV infection
  • 15%- 20% of cases associated with CMML or AML
  • Aggressive clinical course with short survival

  Microscopic Findings

  • In skin, tumor involves dermis and subcutaneous fat with no epidermotropism, angioinvasion or coagulative necrosis
  • Diffuse, dense, monomorphic infiltrate; lack of or few reactive cells in the background
  • Tumor cells:
    • Blastic morphology in most; can be pleomorphic
    • Size: medium
    • Nucleus: single, irregular contours, fine chromatin
    • Nucleolus: absent or indistinct
    • Cytoplasm: scant and gray-blue
    • High mitotic rate

  Immunohistochemistry Staining and Molecular Studies

  • Diagnostic positive markers: CD4, CD43, CD56, CD123
  • Other positive markers: BDCA-2(CD303), CD2, CD2AP, CD7, CD45, CD68, CD117, TCL1, TdT
  • Negative: CD1a, CD3, CD5, CD8, CD19, CD20, CD21, CD23, CD25, CD30, CD34, lysozyme, MPO
  • Lack of TRG@ or IGH@ rearrangement

  Differential Diagnosis

  • B-Cell Lymphoblastic Lymphoma
    • Positive for CD19, PAX5, TdT (diffuse and strong)
    • Negative for CD4, CD56 and CD123
  • T-Cell Lymphoblastic Lymphoma
    • CD1a+, cCD3+ (strong and diffuse), CD56-, CD123-
  • Leukemia Cutis (Particularly with monocytic differentiation; see table below)
    • AML can occur in 15-20% BPDCN
    • Positive for MPO (if myeloid differentiation), lysozyme, CD11c, CD13, CD14
    • Shared markers with BPDCN: CD4, CD7, CD56, CD123, TCL1
    •   Leukemia Cutis (MPO-CD34-)
      Infiltration pattern
      Diffuse, interstitial Diffuse, sheets
      Cell size
      Large Medium
      May be large Absent or indistinct
      Moderate to abundant Minimal
      Mostly positive Positive
      Mostly positive Negative
      Often positive Negative
      Mostly positive Mostly positive
      Often positive (~50%) Positive
      Positive, diffusely and strongly Positive, subset and dot-like
      Rarely positive, weakly Positive, diffusely and strongly
      Rarely positive Mostly positive
  • Cutaneous NK/T-Cell Lymphoma, Nasal-Type
    • Pleomorphic tumor cells, mixed inflammatory background
    • Epidermotropism, marked angioinvasion and necrosis
    • Positive for cCD3, cytotoxic molecules and EBER
    • Shared markers with BPDCN: CD2, CD4, CD56
  • Merkel cell carcinoma
    • Pan-CK+, CK20+, CD56+, CD117+, PAX5+, TdT+
    • Neuroendocrine markers+, Merkel cell polyomavirus+ (80-100%)

Last update: 05/20/2015