Follicular lymphoma
- Lesion
A slow-growing lymphoma of germinal centre B cells that cannot die because they make too much BCL2. It often returns and can turn aggressive.
What it is
Follicular lymphoma is the commonest indolent non-Hodgkin lymphoma in adults. The tumour copies the germinal centre: nodules of centrocytes (small cleaved cells) and centroblasts (large cells). Its hallmark is the t(14;18), which places BCL2 next to the immunoglobulin heavy-chain locus and keeps the cells alive. It usually presents with painless generalized lymphadenopathy and marrow involvement, follows a waxing and waning course, and transforms to DLBCL in a large fraction of patients.
Structure
- Node: crowded, back-to-back nodules of similar size that efface the architecture and extend beyond the capsule.
- Nodules contain mostly centrocytes with angulated, cleaved nuclei and fewer large centroblasts; few mitoses and no tingible-body macrophages.
- Grading reflects the number of centroblasts.
Step by step
- During B-cell development the t(14;18) occurs in a precursor, joining BCL2 to the IGH enhancer.
- Overexpressed BCL2 blocks the apoptosis that normally removes germinal centre cells with low-affinity antibodies.
- Further mutations in epigenetic genes (KMT2D, EZH2) lock in the germinal centre programme.
- Clonal follicles slowly replace nodes, spleen and marrow.
- Additional hits (often MYC) produce transformation to an aggressive large-cell lymphoma.
Reactive follicular hyperplasia vs follicular lymphoma
| Feature | Reactive follicles | Follicular lymphoma |
|---|---|---|
| Architecture | Preserved, follicles spaced out | Effaced by crowded follicles |
| Follicle shape and size | Varied, irregular | Uniform, back to back |
| Tingible-body macrophages and mitoses | Many | Few |
| BCL2 in germinal centre cells | Negative | Positive in most cases |
| Light chains | Mixed κ and λ | One light chain only |
Markers
- CD10
- BCL6
- BCL2
- CD20
- CD5 negative
Clinical notes
- Painless, generalized lymphadenopathy in middle-aged adults; intra-abdominal nodes and spleen common.
- Survival is long but relapses are the rule; therapy is often reserved for symptoms.
Test yourself
Think of the answer, then tap the question to see it.
Which translocation and protein characterize follicular lymphoma?
t(14;18) joining IGH and BCL2, with overexpression of the anti-apoptotic BCL2 protein.
Where does follicular lymphoma usually involve the marrow?
In paratrabecular aggregates, next to the bony trabeculae.
What does follicular lymphoma most often transform into?
Diffuse large B-cell lymphoma.
Elsewhere in DurgiPedia
Connections
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: Non-Hodgkin Lymphoma Treatment (PDQ®)–Patient Version (National Cancer Institute (NCI), 2026).
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Representative model, for educational purposes only.