Lymphomas of the central nervous system
Updates to Article Attributes
Primary CNS lymphoma (PCNSL) are uncommon tumours, accounting for only 1% of malignant CNS tumours. By definition there is no co-existing systemic disease at the time of diagnosis, distinguishing it from CNS involvement from systemic lymphoma (secondary CNS lymphoma).
Epidemiology
Typically patients diagnosed with PCNSL are over the age of 50 with short duration of symptoms (at most a few months) 4. There is a male predominance of approximately 2:1 4. As there is a strong association with HIV/AIDS and other immunocompromised states, demographics in these patients reflects the underlying condition.
Predisposing factors include:
- HIV/AIDS: approximately 2-6% of patients with HIV will develop PCNSL 5
- prior EBV infection
- post transplantation (see: primary central nervous system post-transplant lymphoproliferative disorder)
- IgA deficiency
- Wiskott-Aldrich syndrome
Primary CNS lymphoma accounts for approximately 1% of all extranodal lymphoma, and ~1% of intracranial tumours. Recently there appears to be increasing incidence at least partially due to increasing rates of immunocompromised patients. An An increase is however also seen in the non immunocompromised population.
Clinical presentation
Patients with PCNS lymphoma present similarly to patients with other central nervous system masses; symptoms and signs of raised intracranial pressure, focal neurological disorders and seizures.
Pathology
Typically PCNSL present as multiple, infiltrating mass lesions that can arise in cortex, white matter or deep grey matter (more common in low grade lesions 1). They may demonstrate areas of necrosis especially in immunodeficient patients.
The vast majority (>90%) of PCNSL are B cell in origin: diffuse large B-cell lymphoma and high-grade Burkitt-like B-cell lymphoma 1. Malignant cells tend to accumulate around blood vessels.
Low-grade tumours are more frequently T-cell in origin 1.
CSF examination demonstrates elevated protein and decreased glucose. Positive cytology is uncommon (~25%).
Radiographic features
The most helpful imaging pattern, present in a majority of untreated non-immunocompromised patients is of a CT hyperdense enhancing mass, with MRI T1 hypointense, T2 iso- to hypo-intense, vivid homogeneous enhancement and restricted diffusion. Unfortunately this pattern is not always present (see below).
Typically PCNSL are supratentorial (75-85%) 5 and appear as a mass or multiple masses (11-50% 3) that are usually in contact with the subarachnoid/ependymal surfaces. Crossing the corpus callosum is not infrequently seen. Enhancement on both CT and MRI is pronounced and usually homogenous. Even with larger lesions there is little mass effect for size, and limited surrounding vasogenic oedema.
Low grade tumours differ from the more common high-grade PCNSL in several ways 1:
- deep locations and spinal involvement is more common
- contrast enhancement is absent, irregular or only mild
Disseminated meningeal/intraventricular disease is uncommon seen between 1 and 7% if cases at presentation and usually seen in high grade cases 8.
It should be noted that in patients who are immunocompromised (typically HIV/AIDS or post-transplant) appearances are more heterogeneous.
CT
- most lesions are hyperattenuating (70%) 3
- shows enhancement
- haemorrhage is distinctly uncommon
- there are often multiple lesions in patients with HIV/AIDS
MRI
Reported signal characteristics include:
- T1: typically hypointense to white matter
- T1 C+ (Gd): typical high grade tumours show strong homogeneous enhancement while low grade tumours have absent to moderate enhancement 1
-
T2: variable
- majority are iso to
hypo intensehypointense- isointense: 33% 9
- hypointense: 20% 9
- hyperintense: 15-47%, more common in tumours with necrosis 1,9
- majority are iso to
- DWI: typical restricted diffusion
-
MR spectroscopy
- large choline peak
- reversed choline/creatinine ratio
- lactate peak may also be seen 7
- MR perfusion: shows only a modest increase in rCBV, much less marked than in high-grade gliomas, where angiogenesis is a prominent feature
Scintigraphy
Thallium 201
- shows increased uptake
C11 Methionine PET
- shows increased uptake
Treatment and prognosis
Treatment is predominantly with steroids (which can dramatically shrink the tumour) and chemotherapy (high dose methotrextatemethotrexate) with or without whole brain irradiation 4.
If the tumour is low grade (uncommon: see above) then local treatment with surgical resection and radiotherapy may be effective 1 and long term survival is possible.
The tumours are often high grade and despite treatment have a poor prognosis. If only surgical resection is performed then death occurs within a few months. With high dose chemotherapy the tumour can be significantly reduced in size, however recurrence is common, with median survival of around 30 months 1. Those who are immunocompromised (e.g. HIV positive) do worse.
Differential diagnosis
For general imaging appearencsappearances on CT and MRI consider:
-
secondary CNS lymphoma:
indisguishableindistinguishable on imaging -
cerebral toxoplasmosis: see toxoplasmosis vs lymphoma
- toxoplasmosis does not exhibit subependymal spread
- more likely to lie in basal ganglia, corticomedullary junction
- CNS lymphoma is thallium/PET avid, whereas toxoplasmosis is not
-
butterfly glioma/GBM
- more commonly centrally necrotic
- tumefactive MS/ADEM
-
cerebral abscess
- peripheral enhancement of PCNSL is thicker 3
- central restricted diffusion
- neurosarcoidosis 4
-</ul><p>Primary CNS lymphoma accounts for approximately 1% of all extranodal lymphoma, and ~1% of intracranial tumours. Recently there appears to be increasing incidence at least partially due to increasing rates of immunocompromised patients. An increase is however also seen in the non immunocompromised population.</p><h4>Clinical presentation</h4><p>Patients with PCNS lymphoma present similarly to patients with other central nervous system masses; symptoms and signs of raised intracranial pressure, focal neurological disorders and seizures.</p><h4>Pathology</h4><p>Typically PCNSL present as multiple, infiltrating mass lesions that can arise in cortex, white matter or deep grey matter (more common in low grade lesions <sup>1</sup>). They may demonstrate areas of necrosis especially in immunodeficient patients.</p><p>The vast majority (>90%) of PCNSL are B cell in origin: diffuse large B-cell lymphoma and high-grade Burkitt-like B-cell lymphoma <sup>1</sup>. Malignant cells tend to accumulate around blood vessels.</p><p>Low-grade tumours are more frequently T-cell in origin <sup>1</sup>. </p><p>CSF examination demonstrates elevated protein and decreased glucose. Positive cytology is uncommon (~25%).</p><h4>Radiographic features</h4><p>The most helpful imaging pattern, present in a majority of untreated non-immunocompromised patients is of a CT hyperdense enhancing mass, with MRI T1 hypointense, T2 iso- to hypo-intense, vivid homogeneous enhancement and restricted diffusion. Unfortunately this pattern is not always present (see below). </p><p>Typically PCNSL are supratentorial (75-85%) <sup>5</sup> and appear as a mass or multiple masses (11-50% <sup>3</sup>) that are usually in contact with the subarachnoid/ependymal surfaces. Crossing the <a href="/articles/corpus-callosum">corpus callosum</a> is not infrequently seen. Enhancement on both CT and MRI is pronounced and usually homogenous. Even with larger lesions there is little mass effect for size, and limited surrounding vasogenic oedema. </p><p>Low grade tumours differ from the more common high-grade PCNSL in several ways <sup>1</sup>:</p><ul>- +</ul><p>Primary CNS lymphoma accounts for approximately 1% of all extranodal lymphoma, and ~1% of intracranial tumours. Recently there appears to be increasing incidence at least partially due to increasing rates of immunocompromised patients. An increase is however also seen in the non immunocompromised population.</p><h4>Clinical presentation</h4><p>Patients with PCNS lymphoma present similarly to patients with other central nervous system masses; symptoms and signs of raised intracranial pressure, focal neurological disorders and seizures.</p><h4>Pathology</h4><p>Typically PCNSL present as multiple, infiltrating mass lesions that can arise in cortex, white matter or deep grey matter (more common in low grade lesions <sup>1</sup>). They may demonstrate areas of necrosis especially in immunodeficient patients.</p><p>The vast majority (>90%) of PCNSL are B cell in origin: diffuse large B-cell lymphoma and high-grade Burkitt-like B-cell lymphoma <sup>1</sup>. Malignant cells tend to accumulate around blood vessels.</p><p>Low-grade tumours are more frequently T-cell in origin <sup>1</sup>. </p><p>CSF examination demonstrates elevated protein and decreased glucose. Positive cytology is uncommon (~25%).</p><h4>Radiographic features</h4><p>The most helpful imaging pattern, present in a majority of untreated non-immunocompromised patients is of a CT hyperdense enhancing mass, with MRI T1 hypointense, T2 iso- to hypo-intense, vivid homogeneous enhancement and restricted diffusion. Unfortunately this pattern is not always present (see below). </p><p>Typically PCNSL are supratentorial (75-85%) <sup>5</sup> and appear as a mass or multiple masses (11-50% <sup>3</sup>) that are usually in contact with the subarachnoid/ependymal surfaces. Crossing the <a href="/articles/corpus-callosum">corpus callosum</a> is not infrequently seen. Enhancement on both CT and MRI is pronounced and usually homogenous. Even with larger lesions there is little mass effect for size, and limited surrounding vasogenic oedema. </p><p>Low grade tumours differ from the more common high-grade PCNSL in several ways <sup>1</sup>:</p><ul>
-<li>majority are iso to hypo intense<ul>- +<li>majority are iso to hypointense<ul>
-</h6><ul><li>shows increased uptake</li></ul><h6>C<sup>11 </sup>Methionine PET</h6><ul><li>shows increased uptake</li></ul><h4>Treatment and prognosis</h4><p>Treatment is predominantly with steroids (which can dramatically shrink the tumour) and chemotherapy (high dose methotrextate) with or without whole brain irradiation <sup>4</sup>.</p><p>If the tumour is low grade (uncommon: see above) then local treatment with surgical resection and radiotherapy may be effective <sup>1</sup> and long term survival is possible.</p><p>The tumours are often high grade and despite treatment have a poor prognosis. If only surgical resection is performed then death occurs within a few months. With high dose chemotherapy the tumour can be significantly reduced in size, however recurrence is common, with median survival of around 30 months <sup>1</sup>. Those who are immunocompromised (e.g. HIV positive) do worse.</p><h4>Differential diagnosis</h4><p>For general imaging appearencs on CT and MRI consider:</p><ul>- +</h6><ul><li>shows increased uptake</li></ul><h6>C<sup>11 </sup>Methionine PET</h6><ul><li>shows increased uptake</li></ul><h4>Treatment and prognosis</h4><p>Treatment is predominantly with steroids (which can dramatically shrink the tumour) and chemotherapy (high dose methotrexate) with or without whole brain irradiation <sup>4</sup>.</p><p>If the tumour is low grade (uncommon: see above) then local treatment with surgical resection and radiotherapy may be effective <sup>1</sup> and long term survival is possible.</p><p>The tumours are often high grade and despite treatment have a poor prognosis. If only surgical resection is performed then death occurs within a few months. With high dose chemotherapy the tumour can be significantly reduced in size, however recurrence is common, with median survival of around 30 months <sup>1</sup>. Those who are immunocompromised (e.g. HIV positive) do worse.</p><h4>Differential diagnosis</h4><p>For general imaging appearances on CT and MRI consider:</p><ul>
-<a href="/articles/secondary-cns-lymphoma">secondary CNS lymphoma</a>: indisguishable on imaging</li>- +<a href="/articles/secondary-cns-lymphoma">secondary CNS lymphoma</a>: indistinguishable on imaging</li>
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