Burkitt's lymphoma (or "Burkitt's tumor", or "Malignant lymphoma, Burkitt's type") is a cancer of the lymphatic system (in particular, B lymphocytes). It is associated with the Epstein-Barr virus, also the cause of mononucleosis as well as other cancers. It is named after Denis Parsons Burkitt, a surgeon who first described the disease in 1956 while working in equatorial Africa.
Children affected with the disease often also had chronic malaria which is believed to have reduced resistance to the virus. This is known as classical African or endemic Burkitt's lymphoma. Disease characteristics include large tumors in the facial or abdominal regions.
Outside of central Africa, a type of non-Hodgkin lymphoma is found where cancer cells have a similar appearance to the cancer cells of classical African or endemic Burkitt's lymphoma. This condition is known as the non-African or sporadic type of Burkitt's lymphoma. Again it is believed that impaired immunity provides an opening for development of the Epstein-Barr virus. Examination of chromosomes in this tumor shows translocation of the myc gene with an Ig gene is seen in this lymphoma, commonly.
Currently Burkitt's lymphoma can be divided into three main clinical variants: the endemic, the sporadic and the immunodeficiency-associated variants. Burkitt's lymphoma is usually associated with over 90% of AIDS cases.
By morphology (i.e. microscopic appearance) or immunophenotype, it is almost impossible to differentiate these three clinical variants. Immunodeficiency-associated Burkitt lymphoma may demonstrate more plasmacytic appearance or more pleomorphism, but these features are not specific.
Of all cancers involving the same class of blood cell, 2% of cases are Burkitt's lymphoma.
The tumor consists of sheets of a monotonous (i.e. similar in size and morphology) population of medium size lymphoid cells with high proliferative activity and apoptotic activity. The "starry sky" appearance seen under low power is due to scattered tingible body-laden macrophages (macrophages containing dead body of apoptotic tumor cells). The old descriptive term of "small non-cleaved cell" is misleading. The tumor cells are mostly medium in size (i.e. tumor nuclei size similar to that of histiocytes or endothelial cells). "Small non-cleaved cells" are compared to "large non-cleaved cells" of normal germinal center lymphocytes. Tumor cells possess small amount of basophilic cytoplasm. The cellular outline usually appears squared off.
Malignant B cell characteristics
Malignant B cells have identical DNA recombinations of the V(D)J region of the Immunoglobin genes. This means that no increase in specificity of Antibody molecules is occurring in the malignant cells. These malignant cells are thus clonal populations and can be assayed for by using DNA probes specific for the regions where recombination is expected. Normal DNA will be characterized by two high concentration of identical germ line DNA V(D)J regions and endless, likely undetectable, non-germline Ig V(D)J DNA. Lymphoma cells have an additional high concentration of V(D)J DNA that is unlike the germline, indicating clonal populations of B Cells that are not undifferentiated B Cells (Germline DNA cells). Assays typically use the process of Electrophoresis and southern blot analysis to determine the existence of these characteristics.
Treatment includes dose-adjusted EPOCH with Rituxan (rituximab).
Effect of the chemotherapy, as with all cancers, depends on the time of diagnosis. With faster growing cancers, such as Burkitt's, the cancer actually responds faster than with slower growing cancers. This rapid response to chemotherapy can be hazardous to patient, as a phenomenon called "tumor lysis syndrome" could occur. Close monitoring of patient and adequate hydration is essential during the process.
Other treatments are immunotherapy, bone marrow transplants, surgery to remove the tumor, and radiotherapy.
Treatment with dose-adjusted EPOCH with Rituxan (rituximab) has shown an 8 year survival rate of 91% for low risk, 90% for low-intermediate risk, 67% for high-intermediate risk, and 31% for high risk cases with few of the side effects associated with Burkitt's lymphoma chemotherapy.