September 24, 2023

What is CD34?

CD34 is a protein normally produced by endothelial cells (the cells that line the inside of blood vessels), immature (developing) immune cells, and supporting connective tissue cells. It can also be produced by some types of tumour cells. Pathologists use a test called immunohistochemistry to see cells producing this protein under the microscope.

What does CD34 do?

The exact function of CD34 is still being investigated. However, studies suggest that this protein helps promote the development of stem cells, supports the movement of cells, and helps cells stick together.

What types of cells normally express CD34?

CD34 is normally expressed by several different types of cells throughout the body. These include:

  • Endothelial cells – These are the cells that line the inside of blood vessels throughout the body.
  • Hematopoietic progenitor cells – These are immature cells that will later become part of the immune system.
  • Fibroblasts – Fibroblasts are found all over the body. They are support cells that help hold the body together. They also help heal the body after injury.

What types of tumours express CD34?

Almost all tumours that arise from endothelial cells or contain blood vessels will express CD34. Most types of tumours that contain fibroblasts or where the tumour cells show fibroblastic differentiation will also express CD34. Some types of immune system cancers, in particular those made up of immature immune cells, will also express this protein.

Some examples of CD34 expressing tumours:


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