Primary central nervous system lymphomas in immunocompetent patients.

Primary Central nervous system lymphoma is a rare non-Hodgkin's tumor of the brain that has been traditionally found in patients with immunodeficiency syndromes. However, there are several immunocompetent patients that have also been reported with this neoplasm. In this group of patients, the mean age of diagnosis is around 60-year old, with a very slight predominance in women. Macroscopically, most of the tumors are unique and mainly located in the supratentorial region in the proximity of the cerebrospinal fluid circulation. The typical histological pattern is a perivascular distribution of tumor cells, within a network of reticulin fibers. Even though they are usually well defined masses, it is not rare to find tumor invasion beyond the macroscopic margin. Coagulative necrosis is not as common as in immunodeficiency-related cases. Immunohistochemistry has demonstrated that most of the tumor cells are B-lymphocytes and the electron microscopic findings do not differ from those reported in systemic non-Hodgkin's lymphomas. There are several histological classifications of these tumors, some of them with recent modifications to facilitate the analysis, but unfortunately, up now with a little or no clinical significance. The diagnosis is based on the histological study of the specimen obtained mainly through a Stereotactic biopsy. The treatment is based on a combination of chemotherapy followed by radiotherapy, but the mortality rate is still high.