Primary CNS lymphomas

Published on 19/03/2015 by admin

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Last modified 19/03/2015

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41

Primary CNS lymphomas

CNS lymphomas may be primary or secondary:

Some lymphomas are epidural or vertebral in location and impinge on the CNS through mass effect or vertebral collapse. Plasmacytomas and multiple myeloma in the thoracic and cervical vertebrae are common examples. Mediastinal lymphomas, many of which are high grade B cell neoplasms, can also cause spinal cord compression.

image CONDITIONS ASSOCIATED WITH PCNSL

There is no universally accepted scheme for classifying lymphomas, though the REAL and WHO classifications are commonly used. As extra-nodal lymphomas, CNS lymphomas have been difficult to incorporate into these classifications, and their origins largely remain obscure.

Many CNS lymphomas respond rapidly to steroid therapy. Although this effect is transient, widespread apoptosis of lymphoma cells results in a marked reduction in tumor mass. Such shrinkage can compromise the yield of stereotactic biopsies and apoptosis their diagnostic use. Early biopsy is therefore recommended.

Cytologic examination of the cerebrospinal fluid (CSF) is often useful for both preliminary assessment and follow-up of the patient.

image EPIDEMIOLOGIC AND CLINICAL ASPECTS OF PCNSL

image PCNSL accounts for 2–4% of intracranial neoplasms.

image PCNSL accounts for approximately 1% of non-Hodgkin’s lymphomas.

image The incidence of PCNSL in both immunocompetent and immunocompromised patient groups has increased since 1985, but lifetime risk in HIV-positive patients has declined since the introduction of HAART.

image Peak incidence is seen in the sixth and seventh decades in immunocompetent patients and in the fourth decade in immunocompromised patients.

image PCNSL is more common in males than females (3:2 ratio), particularly among immunodeficient patients, in whom the ratio approaches 10:1.

image T cell PCNSL presents in a younger age group than B cell PCNSL.

image PCNSL presents as a space-occupying lesion causing raised intracranial pressure, focal neurologic deficit, or epilepsy.

image Angiotropic large-cell lymphoma presents with fluctuating confusion, transient ischemic attacks, or a rapid dementia.

image PCNSL is evident as irregular, sometimes multifocal, contrast-enhancing masses on CT or MRI.

image The radiologic appearances of PCNSL may mimic a high grade glioma or toxoplasmosis in immunocompromised patients.

image A poor prognosis is characteristic despite a reported increase in median survival in some studies that have used combination radiotherapy and chemotherapy.

image There is a poorer prognosis in patients over 60 years of age and in those with a preoperative Karnovsky score of <70, a family history of cancer in first-degree relatives, or an immunocompromised status.

image Survival does not appear to be correlated with histologic features.

MICROSCOPIC APPEARANCES

Many PCNSLs are characterized by sheets of lymphoma cells separated by areas of necrosis. The cells tend to invade the walls of small cerebral blood vessels and accumulate in perivascular spaces (Fig. 41.3). This produces a characteristic lacy pattern of reduplicated perivascular reticulin (Fig. 41.4), which is evident even in necrotic tissue. Small-cell PCNSLs tend to be more infiltrative and less necrotic than large-cell PCNSLs. At its infiltrative edge, PCNSL diffusely invades CNS tissue, mimicking a glioma (Fig. 41.5). Like some neuroepithelial neoplasms, PCNSL also spreads through the subarachnoid space and invades the pial surface of the brain. Meningeal and intraventricular spread can be extensive (Fig. 41.6, see also Fig. 41.2b).

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