Burkitt Lymphoma

Overview
  • Burkitt Lymphoma is a highly aggressive histological subtype of Non-Hodgkin Lymphoma (NHL) and occurs in three different forms: sporadic, endemic, and immunodeficiency-associated. Although all of these forms share the same molecular pathogenesis, nearly all cases of the endemic form, and a proportion of the immunodeficiency-associated form, are associated with EBV infection, suggesting a possible role for this virus in the pathogenesis of the malignancy in these populations.
Epidemiology
  • The epidemiology of Burkitt Lymphoma is complex. In equatorial Africa, the disease is quite common, with onset before age 15 and representing nearly 20% of all cancers in children. Outside of Africa, the disease occurs in a slightly older population, with typical onset in the 30s. The sporadic form is quite rare and represents only 1% of all Non-Hodgkin Lymphomas. There is an increased risk among immunocompromised patients, especially those with AIDS.
Pathogenesis
  • Whatever the patient population, the genetic event which ultimately initiates transformation in Burkitt Lymphoma appears to be a translocation between Chromosome 8 and 14, t(8;14), placing the myc oncogene under the promoter of the heavily-expressed immunoglobulin heavy chain gene. Over-expression of myc results in uncontrolled cell growth and thus transformation of the B-cell clone.
  • A strong pathogenic connection appears to exist between EBV infection and Burkitt Lymphoma in the endemic and immunodeficiency-associated forms of the neoplasm. The precise mechanism by which EBV encourages neoplastic transformation of B-cells is unclear and likely multi-factorial. EBV virus itself induces proliferation of B-cells and this may contribute although others speculate that the chronic inflammatory environment engendered by EBV viral infection may be more pathogenic. Whatever the case, EBV infection appears to increase the probability of the etiopathogenic t(8;14) translocation described above.
Morphology
  • Histologically, Burkitt Lymphoma presents as sheets of monotonous B-cells with a high mitotic rate, many of which are undergoing apoptosis. Scattered within the tumor are non-neoplastic macrophages in the process of phagocytosing apoptotic nuclear debris, giving the tumor a characteristic "starry sky" pattern.
Clinical Consequences
  • Burkitt Lymphoma almost always arises in extranodal sites, that is, outside of lymph nodes. The endemic form typically arises facial bones, especially the mandible, while the sporadic and immunodeficiency-associated forms often arise as an abdominal mass.
  • Burkitt Lymphomas are highly aggressive with rapid proliferative rates; however, they are also extremely susceptible to chemotherapeutics and thus high remission rates can be achieved in the modern era.