The etiology of non-Hodgkin lymphoma, as well as its global dramatic rise in incidence during the past decades, remains largely unexplained. However, there is increasing awareness that this group of malignancies may entail not only clinical, morphological and molecular heterogeneity, but also considerable variations in terms of etiologic factors. In this review, epidemiologic patterns are summarized as well as current evidence of associations between various known or suspected risk factors for non-Hodgkin lymphoma overall or for any of its subtypes. Central pathogenetic mechanisms include immunosuppression, especially in relation to T-cell function and loss of control of latent EBV infection, and chronic antigen stimulation. Some degree of familiar aggregation also implies a role for genetic susceptibility. A number of recent investigations of non-Hodgkin lymphoma etiology will hopefully lead to a better understanding of the causes of these malignancies.

SUMMARY BackgroundRegional studies on inflammatory bowel disease (IBD) suggest an increasing prevalence over time, but no nationwide estimate has been published so far.

A proportion of classical Hodgkin lymphoma (HL) is believed to be causally related to infection with the ubiquitous lymphotropic EBV. The determining factors for development of EBV-related HL remain poorly understood, but likely involve immunological control of the viral infection. Accordingly, markers of the HLA class I region have been associated with risk of EBV-related HL. To study the host genetic component of EBV-related HL further, we investigated the lymphoma's association with HLA-A*01 and HLA-A*02 simultaneously in the setting of infectious mononucleosis (IM), a risk factor for EBV-related HL, in a case-series analysis including 278 EBV-related and 656 EBV-unrelated cases of HL. By logistic regression, HLA-A*01 alleles [odds ratio (OR) per allele, 2.15; 95% CI, 1.60-2.88] were associated with increased and HLA-A*02 alleles (OR per allele, 0.70; 95% CI, 0.51-0.97) with decreased risk of EBV-related HL. These allele-specific associations corresponded to nearly 10-fold variation in risk of EBVrelated HL between HLA-A*01 and HLA-A*02 homozygotes. History of IM was also associated with risk of EBV-related HL (OR, 3.40; 95% CI, 1.74-6.66). The association between history of IM and EBV-related HL was not seen in the presence of HLA-A*02 because this allele appeared to neutralize the effect of IM on EBV-related HL risk. Our findings suggest that HLA class I-restricted EBV-specific cytotoxic T-cell responses and events in the early immune response to EBV infection in IM play critical roles in the pathogenesis of EBV-related HL.case series | epidemiology

Objectives: This study aims to characterize the epidemiology of immunocompetent Primary central nervous system lymphoma (PCNSL) diagnosed 2000-2013 in Sweden.Methods: Cases were identified in the population-based Swedish Lymphoma Register.Incidence per 100 000 person-years and 95% confidence intervals (CI) were calculated, and PCNSL-specific survival was estimated using relative survival. Tests for temporal trends were performed using Poisson regression. Population incidence of all brain tumors was retrieved for comparison.Results: With 359 identified PCNSL cases (median age 66 years), overall incidence was 0.26 (95% CI: 0.24-0.29) and the average annual increase 4% (P = .002). The increasing trend was primarily observed among elderly individuals (70+ years). Similarly, an increase in incidence of all brain tumors was noted only among the elderly. There was no significant improvement in relative survival across the study period although, among fit patients (with Eastern Cooperative Oncology Group, EGOC 0), survival plateaued 6 years after diagnosis. Conclusion:The increasing PCNSL incidence in the elderly was consistent with an increasing incidence of brain tumors of any type and may in part be attributable to improved diagnostics and reporting in this group. New treatment options have not yet translated into general survival improvements in a population-based setting, although the presence of long-term survivors among fit patients is encouraging. K E Y W O R D Scentral nervous system neoplasms, epidemiology, incidence, lymphoma, survival