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Key words: epidemiology, non-Hodgkin's lymphoma, primary CNS lymphoma
Summary
In the beginning of the nineties the National Cancer Institute Surveillance, Epidemiology, and End Results Program calculated the incidence of primary central nervous system non-Hodgkin's lymphoma (PCNSL) as 1 : 100 000. The incidence of PCNSL has been increasing since the seventies in immunocompetent patients. The main increase, however, is taking place since the mid-eighties and is due to the increase of immunodeficieny and immunosuppression. The risk is 2-6% in AIDS patients according to clinical data and will probably further increase with the length of survival in these patients. Transplant patients carry a risk of 1-5% to develop a PCNSL. The risk is 1-2% for renal, and 2-7% for cardiac, lung or liver transplant recipients. Patients with congenital immune deficiency have a risk of 4%. PCNSL may also present as a secondary malignancy.
Introduction
Primary CNS lymphomas (PCNSL) are extranodal non-Hodgkin's lymphomas (NHL). They are histopathologically undistinguishable from NHL of other sites of the body [1]. Epidemiological analyses have to consider that only by the beginning of the eighties neuropathologists confirmed the identity of the so-called microglioma and PCNSL [2].
General trends
According to National Cancer Institute data the incidence of PCNSL rose from 0.027 to 0.075 : 100 000 from 1973 through 1983 [2]. This increase was seen in all age groups and in both sexes and holds true after exclusion of never-married men as a major risk group for AIDS. Also, its beginning antedates the AIDS epidemic. Part of the increase may be an artifact of improvement in diagnostic tools but most of the increase antedates the widespread use of CT. The incidence rate ratios of PCNSL and glioblastoma has risen from 1 : 250 in 1974 to 1 : 36 in 1980, and to 1 : 6 for the years from 1981 to 1990 [2,3]. Systemic nonHodgkin's lymphoma (NHL) has also increased but to a much lesser extent [2]. Many groups have reported a further increase of PCNSL during the eighties and early nineties in immunocompetent patients [4-7]. Our own observations are given in Table 1. There is a dramatic increase of PCNSL due to immunodeficiency and immunosuppression [8-10]. Recent National Cancer Institute data show a significant increase of PCNSL during the...