Lymphomatous involvement of the central nervous system.

Lymphoma may arise within the central nervous system (CNS), known as primary CNS lymphoma (PCNSL) or may involve the CNS secondary to systemic disease. Clinical features are non-specific. A provisional diagnosis of PCNSL can be made on imaging, potentially changing the management algorithm from neurosurgical resection to biopsy. PCNSL in immunocompetent patients generally presents late, is solid, is bright on diffusion weighted imaging and shows uniform enhancement. Contiguity with a cerebrospinal fluid (CSF) surface and perivascular enhancement are useful clues. Immunocompromised patients, on the other hand, present earlier and often have multiple, necrotic, haemorrhagic lesions with irregular or rim enhancement. Secondary CNS involvement predominantly affects the leptomeninges. This review illustrates the varied imaging features of CNS lymphoma, atypical presentations, and differential diagnoses.