Primary CNS lymphoma

Case contributed by Bruno Di Muzio


Recurrent falls. On heavy alcohol abuse.

Patient Data

Age: 70-year-old
Gender: Female

CT Brain


Pre and post-contrast CT images showing a spontaneously hyperdense and homogeneously enhancing mass centered in the right thalamus extending into the right cerebral peduncle, with no clear limits within the right posterior cerebral artery. There is local mass effect. It is not possible to exclude the possibility of a large aneurysm, further CT exam is recommended. 

CTA Circle of Willis


Dynamic scans have been performed and viewed in multiplanar reformats.

The enhancing mass within the right thalamus and hypothalamus is not an aneurysm.

No vascular abnormality is demonstrated.

Conclusion: No evidence of aneurysm. The appearances on the CT scan from Regional Imaging LRH are suggestive of a thalamic enhancing mass with associated edema. Further evaluation with MRI scan recommended.

MRI Brain


Image quality is mildly degraded by motion artefact.

Extensive abnormality consisting of a homogeneously enhancing mass centered in the right thalamus extending into the right cerebral peduncle, with a small area of nodular enhancement located just anterior ( genu of internal capsule ), and abnormal FLAIR hyperintensity and expansion extending inferiorly to involve the entire midbrain, the right lateral and dorsal pons, extending to the right superior cerebellar peduncle. Abnormal signal extends across the posterior limb and genu of the right internal capsule and into the right medial temporal lobe. Confluent bilateral periventricular T2 hyperintensities probably in the main due to background chronic small vessel ischemia, although there is hyperintensity of the genu of the corpus callosum.

The main enhancing component has dimensions of 2.8 x 2.5 x 2.6 cm, and the more anterior regularly nodular enhancing region measures 1.3 x 1 x 0.9 cm. This region demonstrates diffusion restriction and cerebral blood volume increase. The non-enhancing portion is similar in T2 intensity to grey matter.

There is mass effect upon the 3rd ventricle which is partially effaced. No convincing evidence of obstructive hydrocephalus.

MRV is unremarkable with a dominant right transverse sinus.

No aneurysm or vascular stenosis. The right ACA is dominant.

The extracranial structures are unremarkable.

Conclusion: Findings are most consistent with a primary CNS lymphoma rather than GBM in view of the enhancement and T2 signal characteristics (and precontrast density on CT).

Case Discussion

The first images in this case, although atypical, raised the possibility of the lesion be related to an aneurysm, especially for being hyperdense and with a bright enhancement. CTA performed subsequently excluded this hypothesis. On the MRI, it became clear that it is a solid tumor with a highly cellular component, characterized by its hyperdense aspect on CT and marked restricted diffusion on DWI/ADC. 

The case was histologically proven as a primary CNS lymphoma (PCNSL). 

Typically PCNSL are supratentorial and appear as a mass or multiple masses that are usually in contact with the subarachnoid/ependymal surfaces. On CT most lesions are hyperattenuating and shows homogeneous enhancement. On MRI images, they are typically hypointense to white matter on T1, show strong homogeneous enhancement, iso to hypointense on T2, and with a typical restricted diffusion on DWI/ADC. 


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