CNS primary B-cell lymphoma

Findings

CT demonstrates an intra-axial mass within the left frontal lobe, which demonstrates central hypo attenuation, subfalcine herniation with vasogenic edema, a moderate left-to-right midline shift and mass-effect. MRI shows an enhancing, heterogeneous large left frontal lobe intra-axial mass which extends to the genu of the corpus callosum and lateral ventricle ependymal surface. The mass is isointense on T1, slightly hyper intense on T2 and FLAIR. Increased signal is demonstrated on T2 and FLAIR imaging of the central portion of the mass, most consistent with edema. Diffusion weighted and ADC imaging (not shown) demonstrated some evidence of diffusion restriction. There is intense enhancement of the mass on post-contrast imaging. No acute findings on the chest or abdomen CT images.


Diagnosis: CNS primary B-cell lymphoma


Key points

Primary CNS lymphoma now represents as many as 2% of all intracranial neoplasms, 7-15% of primary brain tumors, and less than 1% of non-Hodgkin lymphomas.
CNS lymphoma affects persons at all ages, with a peak incidence in those aged 40-60 years. Almost all CNS lymphomas are non-Hodgkin B-cell tumors.
MRI is the examination of choice because of its high sensitivity and multiplanar capability. The classic appearance of CNS lymphoma is an isointense to isointense-to-hypo intense nodule or mass on nonenhanced T1-weighted MRIs and isointense-to-hyper intense on corresponding T2-weighted MRIs. On post gadolinium-enhanced T1-weighted MRIs, lymphoma tends to enhance intensely and diffusely. Usually, little or no surrounding vasogenic edema is demonstrated.
Tumor lesions can cross the midline and may appear as a butterfly tumor involving both cerebral hemispheres.
Involvement of the corpus callosum is highly suggestive of CNS lymphoma, but it also occasionally occurs with anaplastic glioma and metastatic neoplasm.