Stains & CD markers
CD123


Last staff update: 11 July 2022

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PubMed Search: CD123

Narittee Sukswai, M.D.
Joseph Khoury, M.D.
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Cite this page: Sukswai N, Khoury J. CD123. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cdmarkerscd123.html. Accessed August 14th, 2022.
Definition / general
  • Interleukin 3 receptor alpha chain (IL3Rα)
  • Upregulated and overexpressed in a variety of myeloid and lymphoid neoplasms
  • CD123 is a biomarker for targeted therapy
Essential features
  • CD123 serves as a diagnostic, prognostic and therapeutic marker in some hematologic malignancies, especially acute leukemia
  • CD123 and TCF4 coexpression by immunohistochemistry is highly specific and sensitive for blastic plasmacytoid dendritic cell neoplasm (BPDCN)
Terminology
  • IL3Rα
Pathophysiology
  • Membrane receptor that heterodimerizes with the β common (βc) subunit to constitute the functional IL3 receptor (IL3R)
  • IL3R is the IL3 specific member of the beta βc family of receptors, which also includes IL5R and granulocyte monocyte colony stimulating factor (GM CSF) receptor
  • Functions in regulating growth, proliferation, survival and differentiation of hematopoietic cells, along with immunity and inflammatory response
  • Downstream signaling is primarily through JAK / STAT, RAS / MAPK and phosphatidylinositol 3 kinase pathways (Cancers (Basel) 2020;12:3087)
Clinical features
Interpretation
  • Strongest level of CD123 staining is on plasmacytoid dendritic cells
  • CD123 is expressed by endothelial cells
  • CD123 is a membrane bound protein, resulting in a membranous pattern of staining by immunohistochemistry and surface expression by flow cytometry
  • Reference: Am J Surg Pathol 2019;43:1429
Uses by pathologists
Prognostic factors
  • Prognostic impact of CD123 expression has not been established
Microscopic (histologic) images

Contributed by Joseph Khoury, M.D.
Tonsil

Tonsil

Blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm

Positive staining - normal
  • Hematopoietic stem cells
  • Endothelial cells
  • Plasmacytoid dendritic cells
Positive staining - disease
Negative staining
  • Lymphoma
  • Carcinoma
  • Various soft tissue neoplasms
  • Merkel cell carcinoma
Board review style question #1
Patient presents with a skin tumor comprised of blastoid neoplastic cells involving the dermis and subcutaneous tissue without epidermotropism. Which immunohistochemical profile suits the diagnosis of blastic plasmacytoid dendritic cell neoplasm?

  1. AE1 / AE3 positive, chromogranin positive
  2. CD21 positive, CD23 positive
  3. CD34 positive, MPO positive
  4. TCF4 / CD123 positive, CD4 positive, CD56 positive, CD303 positive
Board review style answer #1
D. TCF4 / CD123 dual stains are highly sensitive and specific to blastic plasmacytoid dendritic cell neoplasm. Such staining is rarely encountered in other malignancies.

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