Chronic lymphocytic leukaemia (CLL/SLL)
- Lesion
A slow cancer of small mature B cells in older adults. It weakens immunity, can attack the patient's own blood cells, and sometimes turns aggressive.
What it is
CLL and SLL are one disease of small, mature-looking B cells: called CLL when the blood count of clonal cells is high, SLL when nodes dominate. It is the commonest leukaemia of adults in Western countries. The cells live too long rather than divide too fast, helped by BCL2 overexpression and by survival signals in the node. The disease disturbs immunity, causing hypogammaglobulinaemia and autoimmune cytopenias, and can transform into a large-cell lymphoma (Richter syndrome).
Structure
- Node: diffuse effacement by small round lymphocytes with dense chromatin and scant cytoplasm.
- Proliferation centres: pale loose clusters of larger prolymphocytes and paraimmunoblasts with mitoses.
- Blood: many small mature lymphocytes; fragile cells crushed during smear preparation become smudge cells.
- Marrow, spleen and liver are usually infiltrated.
Step by step
- A mature B cell acquires lesions such as del(13q14) that remove brakes on BCL2.
- Increased BCL2 prolongs survival; the clone accumulates slowly.
- Signals through the B-cell receptor and from stromal and T cells in proliferation centres support growth (NF-κB, MYC).
- The clone crowds the marrow and suppresses normal B cells: low immunoglobulins, infections.
- Residual normal B cells can make autoantibodies against red cells and platelets.
- New hits (TP53, MYC) can transform the disease into an aggressive large-cell lymphoma.
Markers
- CD5
- CD23
- CD19
- CD20 (dim)
- BCL2
- ZAP-70
Clinical notes
- Often found by chance on a routine blood count in an older adult; symptoms are fatigue, weight loss, lymphadenopathy and hepatosplenomegaly.
- Course varies from many symptom-free years to aggressive disease; stage and genetics guide prognosis.
- Monoclonal B-cell lymphocytosis is a precursor state with a small yearly risk of progression.
Test yourself
Think of the answer, then tap the question to see it.
Which two markers, together with B-cell markers, define CLL/SLL?
CD5 and CD23.
What are proliferation centres?
Pale clusters of larger, dividing prolymphocytes and paraimmunoblasts in an involved node; pathognomonic of CLL/SLL.
What is Richter transformation?
Progression of CLL/SLL to an aggressive large-cell lymphoma, usually DLBCL, often with a rapidly growing node or spleen.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Chronic Lymphocytic Leukemia Treatment (PDQ®)–Patient Version (National Cancer Institute (NCI), 2026).
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Representative model, for educational purposes only.