HealthTree Logo
search more_vert
person Sign In / Create Account
What Makes it CLL? Looking at Chromosome Deletions
Posted: Feb 15, 2023
What Makes it CLL? Looking at Chromosome Deletions image

A CLL cell is a mutated B-cell that is not capable of doing its normal job of defending the body against invaders like bacteria or viruses. The instructions that tell the cell to die are changed so the ineffective B-cell keeps multiplying. 

This happens because certain parts of the B-cell’s instructions (chromosomes) that tell the cell how to work are deleted or mutated. 

To check for chromosome deletions, a doctor will complete a fluorescence in situ hybridization (FISH) test. 

  • A FISH test is completed by collecting a blood sample from the CLL patient which includes a set of the patient’s full chromosomes. The sample is placed on a glass slide and exposed to a small piece of purified DNA tagged with a fluorescent dye (probe). The fluorescently labeled probe finds and then binds to its matching sequence within the set of chromosomes. With the use of a special microscope, the chromosome location where the fluorescent probe bound can be seen (


The B-cell will be labeled as CLL if part of chromosomes 11q, 13q, or 17p are deleted. Some cells may also have an extra copy of chromosome 12 (q = long arm of the chromosome, p= short arm of the chromosome) (NCCN).

The location and size of the deletion in each chromosome may vary among patients. Patients should create a care plan based on their individual situation with a CLL specialist.

Need help finding a CLL specialist?

Check out HealthTree’s CLL Specialist Directory

The author Megan Heaps

about the author
Megan Heaps

Megan joined HealthTree in 2022. As a writer and the daughter of a blood cancer patient, she is dedicated to helping patients and their caregivers understand the various aspects of their disease. This understanding enables them to better advocate for themselves and improve their treatment outcomes. In her spare time, she enjoys spending time with her family. 

Thanks to our HealthTree Community for Chronic Lymphocytic Leukemia Sponsors:


Follow Us

facebook instagram youtube