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A primary CNS lymphoma (PCNSL) is a primary intracranial tumor appearing primarily in patients with severe immunosuppression (typically patients with AIDS). PCNSLs represent around 20% of all cases of lymphomas in HIV infections (other types are Burkitt's lymphomas and immunoblastic lymphomas). Primary CNS lymphoma is highly associated with Epstein-Barr virus (EBV) infection (> 90%) in immunodeficient patients (such as those with AIDS and those iatrogenically immunosuppressed)[1], and does not have a predilection for any particular age group. Mean CD4+ count at time of diagnosis is ~50/uL. Because of the severity of immunosuppression at the time of diagnosis, it is no surprise that prognosis is usually poor. In immunocompetent patients (that is, patients who do not have AIDS or some other immunodeficiency), there is rarely an association with EBV infection or other DNA viruses. In the immunocompetent population, PCNSLs typically appear in older patients in their 50's and 60's. Importantly, the incidence of PCNSL in the immunocompetent population has been reported to have increased more than 10-fold from 2.5 cases to 30 cases per 10 million population[2][3]. The cause for the increase in incidence of this disease in the immunocompetent population is unknown.
[edit] ClassificationMost PCNSLs are diffuse large B cell non-Hodgkin lymphomas[4][5]. [edit] Clinical manifestationsA primary CNS lymphoma usually presents with seizure, headache, cranial nerve findings, altered mental status, or other focal neurological deficits typical of a mass effect[6][7]. Systemic symptoms may include fever, night sweats, or weight loss. [edit] DiagnosisMRI or contrast enhanced CT usually shows multiple (one to three) 3 to 5 cm ring-enhancing lesions in almost any location, but usually deep in the white matter. The major differential diagnosis is cerebral toxoplasmosis, which is also prevalent in AIDS patients and also presents with a ring-enhanced lesion, although toxoplasmosis generally presents with more lesions and the contrast enhancement is more pronounced. Because imaging techniques cannot distinguish the two conditions with certainty, patients usually undergo a brain biopsy if the lesion is solitary or if a trial of toxoplasmosis therapy is non-therapeutic. In the future, it may be possible to use a PCR assay of cerebrospinal fluid for EBV DNA. [edit] TreatmentSurgical resection is usually ineffective because of the depth of the tumor. Treatment with irradiation and corticosteroids often only produces a partial response, but tumor recurs in more than 90% of patients. Median survival is 10 to 18 months in immunocompetent patients, and less in those with AIDS. The addition of IV methotrexate and folinic acid (leucovorin) may extend survival to a median of 3.5 years. If radiation is added to methotrexate, median survival time may increase beyond 4 years. However, radiation is not recommended in conjunction with methotrexate because of an increased risk of leukoencephalopathy and dementia in patients older than 60.[8] In AIDS patients, perhaps the most important factor with respect to treatment is the use of highly active anti-retroviral therapy (HAART), which affects the CD4+ lymphocyte population and the level of immunosuppression. [edit] References
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