CNS Lymphoma

Findings

CT: There is a hyper dense mass in the left frontal lobe with compression of the left lateral ventricle and mild midline shift.
MR: There is a uniformly enhancing hypercellular mass in the medial left frontal lobe, extending to the left basal ganglia. Mass surrounds the left lateral ventricle and has associated cerebral edema best demonstrated along its lateral margin.


Differential diagnosis:
- Lymphoma
- Glioblastoma
- Abscess


Diagnosis: CNS Lymphoma


Key points

Malignant primary CNS neoplasm made up of B lymphocytes
1 – 7% of all primary brain tumors
90% of lesions are supratentorial. Commonly frontal and parietal lobes, periventricular with subependymal involvement.
Presents with neurological symptoms, such as headache or seizure.
Typically occurs in the 5th-6th decade, males greater than females.
Immunocompromised individuals are predisposed to all forms of lymphoma, including the CNS form.
Deep gray nuclei commonly affected.
Like GBM, often involves and crosses the corpus callosum.
On CT, hyper dense and relatively uniform in appearance.

MR:
Lesions tend to be homogeneous iso/hypo intense to cortex on unenhanced T1 and T2 weighted images.
May see "blooming artifact" from blood products or calcium on T2*GRE.
Strong homogeneous enhancement.

Differential considerations:
- GBM enhances heterogeneously, unlike lymphoma.
- Abscess usually has a rim that is hypo intense on T2 weighted images, and reveals restricted diffusion.
- Toxoplasmosis also involves the basal ganglia, but subependymal spread is not an associated finding.
- PMNL is a white matter disease, and is typically non-enhancing.