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Secondary CNS Lymphoma

Summary

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  • Secondary CNS lymphoma (SCNSL) refers to CNS involvement in patients with systemic lymphoma
  • Typically occurs in advanced stages of systemic disease or at relapse
  • Imaging findings include single or multiple enhancing lesions, often with periventricular distribution

Pathophysiology

  • Results from hematogenous spread or direct extension from adjacent structures
  • Most commonly associated with aggressive B-cell non-Hodgkin lymphomas, particularly diffuse large B-cell lymphoma (DLBCL)
  • Disruption of blood-brain barrier facilitates lymphoma cell entry into CNS

Demographics

  • Incidence: 5-10% of patients with systemic lymphoma
  • Risk factors:
    • High-grade lymphomas
    • Advanced stage disease
    • Extranodal involvement
    • Elevated serum LDH levels
  • Median age at diagnosis: 60-65 years
  • Slight male predominance

Diagnosis

  • Clinical presentation:
    • Neurological deficits (e.g., focal weakness, sensory changes)
    • Cognitive impairment
    • Headache
    • Seizures
  • Diagnostic workup:
    • Neuroimaging (MRI with contrast)
    • CSF analysis (cytology, flow cytometry, immunoglobulin gene rearrangement)
    • Brain biopsy (if diagnosis remains uncertain)

Imaging

  • MRI findings:
    • Single or multiple enhancing lesions
    • Periventricular distribution common
    • T1: hypointense to isointense
    • T2/FLAIR: hyperintense
    • Diffusion restriction often present
    • Contrast enhancement: homogeneous or ring-like
  • CT findings:
    • Hyperdense lesions
    • Contrast enhancement
  • Differential diagnosis:
    • Metastases
    • Primary CNS lymphoma
    • Infectious processes (e.g., toxoplasmosis, tuberculoma)

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  • An 80-year old who underwent systemic treatment for a systemic high-grade B cell lymphoma.
  • 6 months later, the patient present with worsening ataxia.
  • MRI showed a right cerebellar lesion with a thick band of peripheral enhancement and diffusion restriction.
  • Biopsy confirmed a CNS relapse of a B cell lymphoma.

Treatment

  • Systemic therapy:
    • High-dose methotrexate-based regimens
    • Rituximab for CD20-positive lymphomas
  • CNS-directed therapy:
    • Intrathecal chemotherapy
    • Whole-brain radiotherapy (WBRT) for extensive disease or palliation
  • Supportive care:
    • Corticosteroids for cerebral oedema
    • Anticonvulsants for seizure control
  • Prognosis:
    • Generally poor, with median survival of 2-6 months without treatment
    • Improved outcomes with aggressive multimodal therapy

Differential diagnosis

Differential Diagnosis Distinguishing Feature
Primary CNS Lymphoma Imaging-identical appearance; periventricular homogeneously enhancing mass with marked diffusion restriction
Metastatic Brain Tumour Often multiple lesions at grey-white matter junction; ring or nodular enhancement; surrounding vasogenic oedema
Glioblastoma Typically single lesion; heterogeneous ring enhancement with central necrosis; infiltrative margins on T2/FLAIR
Multiple Sclerosis Ovoid periventricular lesions; incomplete ring or no enhancement; no mass effect
Cerebral Abscess Ring-enhancing lesion with restricted diffusion in the cavity and elevated signal on DWI; thin smooth enhancing wall
Toxoplasmosis Multiple ring-enhancing lesions in basal ganglia and at grey-white matter junction; restricted diffusion in centre
Progressive Multifocal Leukoencephalopathy Non-enhancing asymmetric subcortical white matter lesions with scalloped margins; no mass effect
Acute Disseminated Encephalomyelitis Bilateral, often large confluent white matter lesions involving grey matter; incomplete ring enhancement
Neurosarcoidosis Leptomeningeal and perivascular enhancement; cranial nerve involvement; hilar lymphadenopathy on chest CT
CNS Vasculitis Multifocal infarcts in multiple vascular territories; vessel wall enhancement on high-resolution MRI