Incidence of primary brain lymphomas is increasing, particularly among immunocompromised patients and older people. Lymphomas tend to infiltrate the brain diffusely, often as multicentric masses adjacent to the ventricles, but may occur as solitary brain masses. Lymphomas may also occur in the meninges, uvea, or vitreous humor. Most are B-cell tumors, often immunoblastic. The Epstein-Barr virus may contribute to development of lymphomas in immunocompromised patients. Most patients do not develop subsequent systemic lymphoma.
MRI can suggest the diagnosis of primary brain lymphoma. However, MRI may be unable to distinguish cerebral toxoplasmosis (which is common among patients with AIDS) or some gliomas from lymphoma, requiring diagnosis by tissue biopsy or CSF cytology.
CSF must be examined to rule out lymphomatous meningitis if there is gadolinium enhancement on MRI or if clinical examination detects evidence of meningeal signs, particularly if cranial neuropathies are detected. In immunocompromised patients, Epstein-Barr virus DNA may be detected in CSF. If CSF does not contain lymphoma cells or Epstein-Barr virus DNA, guided-needle or open biopsy is required. Because lymphoma is initially highly sensitive to corticosteroids, giving these drugs just before biopsy may cause the lesion to disappear, resulting in a false-negative biopsy. Thus, corticosteroids should not be given to patients with suspected CNS lymphoma until after definitive diagnosis, unless absolutely necessary because of acute clinical deterioration.
Staging of primary brain lymphomas involves imaging of the chest, abdomen, and pelvis; slit-lamp examination of the eye; and bone marrow biopsy to determine how far the tumor has spread.
Corticosteroids result in rapid improvement initially, but responses are not durable; primary brain lymphomas typically recur. There is no role for surgical excision except when herniation is impending. Multidrug chemotherapy regimens including high-dose IV methotrexate (1 g/m2 to 8 g/m2) may result in long-lasting responses. The addition of consolidation chemotherapy, consolidation whole-brain radiation therapy, or high-dose chemotherapy with stem-cell rescue may improve survival.
Whole-brain radiation can cause clinically significant leukoencephalopathy, particularly in older patients. This effect may be exacerbated by methotrexate.
Median survival in younger and middle-aged adults is > 5 years.