Primary Central Nervous System Lymphoma

PCNSL (see Cha.pter46 ) develops in approximately 5 percent of patients with AIDS and is found at autopsy in up to 10 percent of cases. It is the initial AIDS-defining illness in 0.6 percent of adults. Primary CNS lymphoma develops in patients with advanced HIV-1 disease who are severely immunosuppressed. The incidence of PCNSL in the AIDS population may be increasing as longevity is extended by medical management and antiretroviral agents. Lymphomas are usually of the diffuse immunoblastic, or diffuse large cell, or small-cell noncleaved B-cell type y] with a predilection for the deep cerebral gray matter, corpus callosum, periventricular white matter, and cerebellar vermis. A relationship to EBV is strongly suggested. EBV is frequently detected in the tumor tissue and detection of EBV DNA by PCR in CSF is sensitive and specific for establishing a diagnosis in the appropriate clinical setting.

Clinical presentation includes headache, mental status changes (confusion, lethargy, memory problems), seizures, cranial nerve palsies, and focal neurological deficits.y , [178] In children, neurological deterioration at times may be rapidly progressive and fulminant. y

Computed tomography and MR characteristics of lymphoma include: (1) hyperdense or isodense mass lesions with variable contrast enhancement; (2) diffusely infiltrating contrast-enhancing lesions; and (3) periventricular contrasting lesions. Surrounding edema is variable, and a large solitary mass may be seen as well as multiple lesions. PCNSL is the most common mass lesion in children and the second most common mass lesion in adults (after toxoplasmosis). The differential diagnosis of intracranial lesions in AIDS patients includes a variety of infectious, neoplastic, and cerebrovascular processes. In adults, the most common mass lesion is toxoplasmosis. Unlike toxoplasma encephalitis, PCNSL lesions may cross the midline in the corpus callosum and be associated with patchy nodular ventricular enhancement. Thallium-201 SPECT scanning (or PET scanning) may be able to distinguish between lymphoma and CNS infections.

Recommendations for the management of intracranial mass lesions in AIDS patients have recently been published. Large lesions with mass effect and threatening impending herniation require open biopsy with decompression. SPECT should be performed when available, because it appears to be highly specific for PCNSL. If the results are positive, stereotactic brain biopsy is warranted for tissue diagnosis. In adults, empiric treatment for toxoplasmosis should be instituted in all other cases except when a single intracranial mass lesion accompanies negative serology for toxoplasmosis. The concomitance of negative toxoplasmosis serology and a single lesion on neuroimaging is deemed sufficient to warrant the performance of a stereotactic biopsy. In children, proceeding directly to stereotactic biopsy may be a consideration to eliminate diagnoses other than OIs.

PCNSL are radiosensitive tumors, but prognosis is extremely poor. '179] , 'W Reduction in tumor size has been noted in patients following whole brain radiation therapy and steroids (400 rad administered over 3 weeks). yj , y,] A 2- to 4-month survival after diagnosis is reported. In general, chemotherapy regimens have not significantly altered long- term survival rates. Prognosis for long-term survival is grim, with death resulting from concurrent illness and OIs rather than lymphoma. Absence of OIs at the time of diagnosis is associated with a longer median survival. Selected patients may be candidates for combined chemotherapy and radiation therapy. W

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