[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [White cells, lymph nodes, spleen and thymus](https://durgical.com/en/general-pathology/areas/hematolymphoid/) › Follicular lymphoma

# 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.

Updated Nov 12, 2026

## Key points

- t(14;18) IGH::BCL2 in most cases; BCL2 protein is expressed in the neoplastic follicles, unlike normal germinal centres.
- Markers: CD19, CD20, CD10, BCL6 and BCL2; CD5 negative (unlike CLL and mantle cell lymphoma).
- Marrow involvement is typically paratrabecular.
- Frequent KMT2D and EZH2 mutations (epigenetic regulators).
- Indolent but hard to cure; histologic transformation, usually to DLBCL, often with MYC gain.

On this page

- The basics Key points
- What it is
- Structure
- Step by step
- Reactive follicular hyperplasia vs follicular lymphoma
- Markers
- Memory aid
- Elsewhere in DurgiPedia

- Clinical Clinical notes

- Study Test yourself

- Connections Connections

## 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.

## Memory aid

Fourteen eighteen: follicles that refuse to die, because BCL2 keeps the lights on.

## 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.

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## Elsewhere in DurgiPedia

- [B-cell activation, class switching and affinity maturation](https://durgical.com/en/immunology/b-cell-activation-class-switching-and-affinity-maturation/)
- [Lymph node: cortex, paracortex, medulla](https://durgical.com/en/immunology/lymph-node-cortex-paracortex-medulla/)

## Connections

## Related 4

- [Evading cell death and replicating without limit: BCL2 and telomerase](https://durgical.com/en/general-pathology/evading-cell-death-and-replicating-without-limit-bcl2-and-telomerase/)
- [Apoptosis: the intrinsic and extrinsic pathways](https://durgical.com/en/general-pathology/apoptosis-the-intrinsic-and-extrinsic-pathways/)
- [Reactive lymphadenitis: the patterns](https://durgical.com/en/general-pathology/reactive-lymphadenitis-the-patterns/)
- [Diffuse large B-cell lymphoma](https://durgical.com/en/general-pathology/diffuse-large-b-cell-lymphoma/)

## Related conditions 1

- [Non-Hodgkin lymphoma](https://durgical.com/en/conditions/non-hodgkin-lymphoma/)

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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: [Non-Hodgkin Lymphoma Treatment (PDQ®)–Patient Version](https://www.cancer.gov/types/lymphoma/patient/adult-nhl-treatment-pdq) (National Cancer Institute (NCI), 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/follicular-lymphoma/