The Common Vein Copyright 2010
Primary CNS lymphoma accounts for 2% of extra-nodal lymphomas, and as in the rest of the body is characterized as an abnormal proliferation of tightly packed neoplastic cells, most often of B-cell origin. Lymphomatous lesions are generally in the supratentorium, most commonly in the cerebral white matter, frontal lesions being most common. They are also seen in the central gray matter and tend to abut the ependyma or meninges. They typically spread along the vascular structures and pathologically involve more tissue than is apparent on gross inspection and seen on imaging. The lesions spread to the leptomeninges and are multifocal almost half of the time, more frequently in the immunocompromised patients. Primary lymphoma is more common than secondary lymphoma which tends to affect the dura. Like glioblastoma, lymphoma can cross the corpus callosum and cause a “butterfly” pattern. Another pattern suggestive of primary lymphoma is the appearance of coating of the ventricles.
Many patients affected with primary CNS lymphoma are immunocompromised, specifically with AIDs, but also including patients with other conditions such as renal transplantation, rheumatoid arthritis or immunoglobulin A deficiency. Although there have been links between Epstein-Barr and cytomegalovirus infections and the development of primary CNS lymphoma in immunocompromised patients with HIV, this has not been demonstrated in primary CNS lymphoma of immunocompetent patients.
Clinically patients present with a wide range of symptoms including those caused by focal mass effect, encephalitis, demyelinating disease, stroke or cranial nerve palsies.
CSF analysis has variable results in confirming the diagnosis, making the diagnosis in 4-44% in immunocompetent patients and 25% of patients with AIDS.
Due to the tightly packed cells within the lymphomatous lesions, they are classically hyperattenuating on CT, when seen. For the same reason, on MRI they can demonstrate decreased T2 signal and restricted diffusion which can help distinguish them from other mass lesions. Virtually all lesions enhance, homogeneously in immunocompetent patients and peripherally in immunocompromised patients. In either case, untreated lymphoma does not demonstrate findings of calcification or hemorrhage. Ventricular seeding can appear as a layer of FLAIR hypointense enhancing tissue.
Surgery has no role in the treatment of CNS lymphoma which is treated with radiation and chemotherapy. Although there is often rapid initial response to radiation and corticosteroids, primary CNS lymphoma always recurs, often in a different location than the primary lesion.
From the Archives of the AFIP: Primary Central Nervous System Lymphoma