What is a cluster of differentiation (CD) and why is it important in HCL?

After your doctor draws your blood, they might do a blood count and analyze the cells. In your doctor's report, you might notice the letters CD followed by numbers (such as CD20 or CD25).

Cluster of differentiation, or CD, refers to molecules on the surface of a cell that are unique to that cell, allowing your doctor to differentiate it from others. Your doctor identifies CD markers on your hairy cells to exclude other diseases and determine with greater accuracy which type of hairy cell leukemia (HCL) you may have.

In HCL, clusters of differentiation (CD) markers can be identified using flow cytometry. How does flow cytometry work? In a lab, doctors stain the cells with highly sensitive and specific antibodies and use a laser to read which markers are present. The laser provides a readout for your doctor to analyze further.

CD25 is an essential marker in HCL because classic HCL is positive for CD25, while HCL variant (HCLv) does not have CD25. The use of flow cytometry to analyze your cells' surface markers can increase your confidence in the accuracy of your diagnosis and help you and your doctor select the best treatment plan. Classic HCL and HCLv often require different treatment.

In past HCLF webinars, presenters, including Drs. Kerry Rogers, Robert Kreitman, and Clive Zent, have discussed identifying CD markers and why this process is important to diagnose HCL and help distinguish classic HCL from HCLv.

You can read more about CD markers in these webinars:

https://www.hairycellleukemia.org/august-2022-webinar

https://www.hairycellleukemia.org/september-2023-webinar

https://www.hairycellleukemia.org/november-2023-webinar