Diagnosis of HIV-related primary central nervous system lymphoma: is there still a role for brain biopsy? A case history.

Certain tumors occur more frequently in Human Immunodeficiency Virus (HlV)-infected individuals: since 1985, high-grade non-Hodgkin's Lymphoma has been an AIDS-defining illness [1]. It has been calculated that at least 5%-10% of HIV-infected individuals develop a lymphoma during the course of the infection [2]. Primary central nervous system lymphomas (PCNSL), which in recent decades have also been undergoing an unexplained increase in incidence in the general population [3], account for up to 25% of all AIDS-associated lymphomas, but early diagnosis of the disease still constitutes a major challenge. Indeed, the imaging characteristic of PCNSL and other mass lesions, of which toxoplasmosis is the one that occurs most frequently in the brain of HIV-positive subjects [4-7], overlap to such a degree that it is nearly impossible to distinguish among the lesions on the basis of their appearance on computed tomography (CT) scan or magnetic resonance imaging (MRI) alone [8]. Nevertheless, early discrimination between PCNSL and toxoplasmosis proffers a unique opportunity to alter the natural history of a neoplasm which, if untreated, has a mortality rate of 75% within 45 days [6, 9, 10].