Primary CNS lymphoma

It is lymphoma confined to the brain, the spinal cord, the fluid around them and the back of the eye, without lymphoma elsewhere in the body.

“Primary” means it started there. This is not lymphoma that spread to the brain from somewhere else, and the distinction matters because the two are treated differently.

Under the microscope it is a diffuse large B-cell lymphoma — the NCI says almost all primary CNS lymphomas are, and a 2024 review puts it at about 95%. Same cells as the commonest lymphoma of all, and almost nothing else in common.

Involvement of the eye is part of what the disease is rather than a complication of it. That is why an eye examination forms part of the assessment.

It is rare. Cancer Research UK puts lymphomas at around 2 in every 100 brain or spinal cord tumours in the UK.

It is most common in people over 60, and slightly more common in men than in women.

A weakened immune system is a recognised risk factor. The 2024 review names immunosuppressive drugs and AIDS; the NCI notes it is increasingly seen in people who are immunocompromised, and that immunosuppression-related cases are almost always associated with Epstein-Barr virus.

That needs a qualifier, and it is an important one. Those statements describe a subgroup. The same sources describe the disease overall as a condition of later life. A diagnosis of primary CNS lymphoma does not imply HIV or any other immune condition, and it should not be read that way by anyone.

None of these sources identifies a cause an individual could have avoided, and nothing here supports a diet, stress or lifestyle explanation.

The sources we read do not report on inheritance or family risk, so we cannot say anything useful about those here.

Symptoms depend entirely on which part of the nervous system is affected, which is why they vary so much from person to person.

Cancer Research UK lists headaches, blurred vision, changes to personality, seizures, and difficulty walking and balancing.

Changes in personality or thinking are worth naming explicitly, because they are frequently the first thing a family notices and frequently the last thing anyone attributes to a lymphoma.

On a scan it appears as a single area in about 60% to 70% of cases, and less often as several.

It grows fast, so symptoms usually develop over weeks rather than months and treatment starts soon after diagnosis.

Treatment starts with high-dose methotrexate rather than the drug combinations used for lymphoma elsewhere in the body. The reason is simple and worth stating plainly: the standard lymphoma regimens do not reach the central nervous system well enough.

The NCI describes high-dose methotrexate as the most frequently used induction outside clinical trials. One combination given a name, MATRix, adds high-dose cytarabine, rituximab and thiotepa.

After that comes consolidation, and there are two routes.

The first is an autologous stem cell transplant — the person’s own stem cells, collected in advance and returned after high-dose chemotherapy. The NCI reports that consolidation with autologous transplant results in a survival advantage for newly diagnosed patients. The conditioning chemotherapy is thiotepa-based; the sources name different combinations, so we are not going to pick one.

The second is radiotherapy to the whole brain. The NCI reports that the standard dose showed significant neurotoxicity, and that a lower dose is considered for people who cannot undergo a transplant.

That is a real trade-off rather than a formality, and it belongs to the person and their treating team. We are describing the options, not recommending one.

Diagnosis requires tissue. The 2024 review is clear that examining a sample under the microscope remains the definitive test, with MRI as the preferred scan.

Induction is hospital-based high-dose methotrexate. That is a materially different experience from the outpatient chemotherapy given for lymphoma elsewhere in the body, and it is fair to expect it to be harder.

Because this is a disease of the brain, the effects of both the lymphoma and the treatment can include thinking, memory and personality. Families often carry more of this than they expected to.

The consolidation decision — transplant or whole-brain radiotherapy — is made with the treating team and depends heavily on fitness and on what matters to the person.

The numbers here are harder than in most of this library. We have stated them rather than softened them, and they describe a group rather than an individual.

The transplant that appears in this disease is autologous — the person’s own cells, collected beforehand and given back. No donor is involved in it.

Neither the NCI summary nor the 2024 review describes any role for a donor transplant in primary CNS lymphoma. We are stating that as what the sources describe, not as a rule that it is never done.

So if you have this diagnosis, or someone you love does, nobody is waiting on a registry search. That is worth being clear about, because the word "transplant" on its own sends people looking.