PBL is defined as lymphoma in the central nervous system (CNS) without primary tumor elsewhere.
It is less common than secondary CNS involvement by systemic lymphoma.
PBL causes approximately 5% of all primary brain tumors [1].
PBL is a diffuse large B-cell lymphoma in 90% of cases and is usually high grade.
Less common PBL histological types are Burkitt’s lymphoma and T-cell lymphoma.
PBL occurs sporadically or in association with congenital or acquired immunodeficiency disorders.
A remarkable increase of PBL incidence was observed in the last decade.
This was mainly due to their association with human immunodeficiency virus infection and partly due to advancement of neuro-imaging techniques.
The etiology of PBL remains unclear: The CNS is devoid of endogenous lymphoid tissue [1].
PBL has been associated with Epstein-Barr virus and cytomegalovirus infection [1-3].
The only established risk factor for PBL is immunodeficiency and PBL is the most common brain tumor in this population.
AIDS accounts for the largest group of immunocompromised patients with primary CNS lymphoma (PCNSL) and is an AIDS-defining diagnosis [1].
Systemic dissemination is unusual and occurs in only 6% of the patients.
Nevertheless complete staging procedures including clinical examination,
computed tomography (CT) of the thorax and abdomen and cerebrospinal fluid examination (CSF) is recommended [4].
A wide variety of clinical presentation is encountered: focal neurologic deficits,
altered mental status,
disturbance of intellectual function,
signs of increased intracranial pressure,
seizure [4].
Since the clinical and neuroimaging presentation of PBL can be varied and the differential diagnostic possibilities are therefore large,
no patient should be treated for PBL without definitive cytological proof of diagnosis,
either by CSF cytology,
or brain biopsy.
Brain biopsy: Stereotactic brain biopsy is the most appropriate method for the diagnosis of PBL.
However,
open brain biopsy may be necessary in those patients who have lesions located in areas of the brain that are difficult to access (eg,
brainstem).
If possible,
the procedure should be performed before corticosteroids have been administered.