CNS lymphoma

Primary CNS lymphoma has association with HIV/AIDS and immunocompromised patients, and does not have systemic nodal disease at diagnosis. It is typically (95%) a B-cell non Hodgkin lymphoma (NHL), and is usually supratentorial (90%), having a predilection for deep grey matter of the frontal and parietallobes, clustering around the ventricles. It also has a predisposition for crossing the corpus callosum, with the differential being a butterfly glioma.

This is in contrast to secondary CNS lymphoma (SCNSL) (also typically NHL) which more commonly involves the leptomeninges but it is uncommonly detectable on CT/MRI

Primary CNS lymphoma accounts for approximately 1% of all extranodal lymphomas, and 1-7% of intracranial tumours but has increasing incidence. This is partially due to increasing rates of immunocompromise but an increase is also seen in the non immunocompromised population.

Epidemiology

• Accounts for 1% of extranodal lymphoma and 1-7%% of intracranial tumors.
• Increasing incidence due to HIV/AIDS and immunocompromised patients but also increasing rates in populations that are not immunocompromised.

Aetiology and Pathogenesis

Classification

Site

• Typically supratentorial (90%)
  • Deep grey matter of frontal and parietal lobes
  • Clusters around ventricles.

Pathology

Macroscopic

• Multiple, infiltrating mass lesions that can arise in cortex, white matter or deep grey matter
• May have areas of necrosis

Microscopic

• B cell in origin (associated with EBV infection)
• Accumulate around blood vessels

Radiological Findings

CT

• Tend to be located in deep grey matter nuclei or periventricular white matter
• Coating ventricles and spread across the corpus callosum are suggestive
• Hyperdense on CT with variable enhancement
• Haemorrhage is distinctly UNCOMMON
• Multiple lesions in patients with HIV/AIDS

MRI

• T1: Hypointense to white matter
• T2: Hypointense to white

Imaging DDx

• Cerebral toxoplasmosis
  • 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
• Tumefactive MS
• Cerebral abscess
• GBM

Laboratory Findings

CSF: elevated protein and decreased glucose, positive cytology rare

Treatment

RRx, Steroids, Chemotherapy

Natural History

• Recurrence following treatment is common, and therefore poor prognosis.