[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Central nervous system](https://durgical.com/en/general-pathology/areas/cns/) › Primary CNS lymphoma

# Primary CNS lymphoma

- Lesion

Primary CNS lymphoma is a B-cell cancer that starts in the brain, eyes or spinal cord, mostly in older adults or people with weak immunity.

Updated Nov 12, 2026

## Key points

- Histology: large atypical B cells cuffing and infiltrating vessel walls (angiocentric pattern) with reticulin rings.
- Markers: CD20 and PAX5 positive, often MUM1 and BCL6; high Ki-67.
- Sites: periventricular white matter and deep grey matter; frequently multiple.
- EBV-positive in immunosuppressed patients; EBV DNA in CSF supports the diagnosis in AIDS.
- Corticosteroids can make the tumour shrink and the biopsy non-diagnostic; biopsy is done before them when possible.
- About one in five patients has eye involvement (vitreoretinal lymphoma).

## What it is

Primary CNS lymphoma is a lymphoma confined to the brain, spinal cord, leptomeninges or eyes, without systemic disease at diagnosis. Almost all are diffuse large B-cell lymphomas that cluster around blood vessels. In immunocompetent patients, mostly older, it is EBV-negative and often driven by MYD88 and CD79B mutations; in AIDS and transplant patients it is EBV-positive. Lesions are often multiple and deep, and can involve the vitreous and retina.

## Structure

- Gross: poorly defined, grey, soft periventricular masses, sometimes with central necrosis in AIDS.
- Reactive T cells and astrocytes surround the tumour; apoptotic bodies and necrosis may be prominent.

## Markers

- CD20
- PAX5
- MUM1
- BCL6
- EBER (in immunosuppressed)
- Ki-67

## Clinical notes

- Cognitive and behavioural changes, focal deficits and seizures; ocular involvement causes floaters and blurred vision.
- Treatment centres on chemotherapy that crosses the blood-brain barrier; surgery has little role.

## Memory aid

Big B cells hugging the vessels around the ventricles; steroids melt them, so biopsy first.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the usual histologic type of primary CNS lymphoma?

Diffuse large B-cell lymphoma with an angiocentric growth pattern.

## Which virus is associated with primary CNS lymphoma in people with AIDS?

Epstein-Barr virus.

## Why can corticosteroids hinder the diagnosis?

They kill lymphoma cells quickly, so the lesion shrinks and a later biopsy may not show the tumour.

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## Elsewhere in DurgiPedia

- [Secondary immunodeficiency: HIV, malnutrition, drugs, asplenia](https://durgical.com/en/immunology/secondary-immunodeficiency-hiv-malnutrition-drugs-asplenia/)

## Connections

## Related 5

- [HIV in the brain and PML](https://durgical.com/en/general-pathology/hiv-in-the-brain-and-pml/)
- [CNS tumours: an overview](https://durgical.com/en/general-pathology/cns-tumours-an-overview/)
- [Intraocular tumours: uveal melanoma and retinoblastoma](https://durgical.com/en/general-pathology/intraocular-tumours-uveal-melanoma-and-retinoblastoma/)
- [Diffuse large B-cell lymphoma](https://durgical.com/en/general-pathology/diffuse-large-b-cell-lymphoma/)
- [Oncogenic viruses and H. pylori: the table to know](https://durgical.com/en/general-pathology/oncogenic-viruses-and-h-pylori-the-table-to-know/)

## Related conditions 3

- [Primary central nervous system lymphoma](https://durgical.com/en/conditions/primary-central-nervous-system-lymphoma/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Non-Hodgkin lymphoma](https://durgical.com/en/conditions/non-hodgkin-lymphoma/)

## Microorganisms 1

- [Epstein–Barr virus](https://durgical.com/en/microbiology/epstein-barr-virus/)

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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: [Primary Central Nervous System Lymphoma Treatment (PDQ®)–Health Professional Version](https://www.cancer.gov/types/lymphoma/hp/primary-cns-lymphoma-treatment-pdq) (National Cancer Institute, 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/primary-cns-lymphoma/