title: Risk factors for primary central nervous system lymphoma: a case-control study.
abstract: BACKGROUND
  The incidence of primary central nervous system lymphoma (PCNSL) has increased over time in both immunocompetent and immunodeficient individuals. The reasons for the increase among immunocompetent patients are unclear.
  
  
  METHODS
  The authors conducted a case-control study of PCNSL at the Mayo Clinic based on cases from local community and referral practices. Cases were all PCNSL patients without immunodeficiency diagnosed between 1975 and 1994 (n = 109). Two groups of controls were selected from the same referral practice, namely, patients with other cancer (cancer controls; n = 101), and patients with a different neurologic disease (neurologic controls; n = 109) seen at our institution during the same time period.
  
  
  RESULTS
  PCNSL was significantly associated with lower education when cases were compared with cancer controls but only suggestively when cases were compared with neurologic controls. PCNSL cases were less likely to have had a history of tonsillectomy or oral contraceptive use compared with both control groups. The findings regarding autoimmune disorders and cardiovascular diseases were inconsistent for the two control groups. Neither farming nor prior personal or family history of cancer appeared to be risk factors for PCNSL.
  
  
  CONCLUSIONS
  The findings of this study warrant further investigation of tonsillectomy and oral contraceptives as possible factors for PCNSL.
authors.affiliation: Department of Neurology, Mayo Clinic and Foundation and the Mayo Cancer Center, Rochester, Minnesota 55905, USA.
authors.forename: D
authors.initials: D
authors.lastname: Schiff
authors.forename: V J
authors.initials: VJ
authors.lastname: Suman
authors.forename: P
authors.initials: P
authors.lastname: Yang
authors.forename: W A
authors.initials: WA
authors.lastname: Rocca
authors.forename: B P
authors.initials: BP
authors.lastname: O'Neill
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016543:Central Nervous System Neoplasms / Q000209:etiology*; D003276:Contraceptives, Oral; D005260:Female; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012307:Risk Factors; D014068:Tonsillectomy
chemical_list: D003276:Contraceptives, Oral