Burkitt's lymphoma

Burkitt lymphoma is a cancer of the lymphatic system, particularly B lymphocytes found in the germinal center. It is named after Denis Parsons Burkitt, the Irish surgeon who first described the disease in 1958 while working in equatorial Africa. The overall cure rate for Burkitt's lymphoma in developed countries is about 90%, but worse in low-income countries. Burkitt's lymphoma is uncommon in adults, where it has a worse prognosis.aggressive: Sézary disease Burkitt lymphoma is a cancer of the lymphatic system, particularly B lymphocytes found in the germinal center. It is named after Denis Parsons Burkitt, the Irish surgeon who first described the disease in 1958 while working in equatorial Africa. The overall cure rate for Burkitt's lymphoma in developed countries is about 90%, but worse in low-income countries. Burkitt's lymphoma is uncommon in adults, where it has a worse prognosis. Currently, Burkitt lymphoma can be divided into three main clinical variants: the endemic, the sporadic, and the immunodeficiency-associated variants. 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. Burkitt's lymphoma is commonly associated with the infection of B cell lymphocytes with the Epstein-Barr virus (EBV) and in these cases in considered to be one form of the Epstein-Barr virus-associated lymphoproliferative diseases. The epidemic variant of Burkitt's lymphoma (eBL) is in almost all cases associated with EBV infection. However, the sporadic variant, which afflicts ~1,200 individuals/year in the USA, is associated with the virus in only 10-15% of cases. The immunodeficiency-associated variant of Burkitt's lymphoma strikes 30-40% of individuals with HIV-induced AIDS and rare cases of patients who received a bone marrow or other organ transplant; in the latter cases, individuals have almost always received intensive chemotherapy and therefore are immunodeficient. About 30% of individuals with the immunodeficiency variant are infected with EBV. The fact that some Burkitt's lymphoma cases do not involve EBV allows that many cases of the disease are not caused and/or promoted by EBV, i.e. the virus may be an innocent passenger virus in these cases. However, the almost ubiquitous presence of the virus in the epidemic variant of Burkitt's lymphoma suggests that it contributes to the development and/or progression of this variant. The mutational landscape in BL has recently been found to differ between tumors with and without EBV infection, further strengthening the role of the virus in lymphomagenesis. All types of Burkitt lymphoma are characterized by dysregulation of the c-myc gene by one of three chromosomal translocations. This gene is found at 8q24. Combined, the two less-common translocations, t(2;8)(p12;q24) and t(8;22)(q24;q11), account for the remaining 15% of cases not due to the t(8;14)(q24;q32) translocation. In 2014, it was described that short non-coding RNAs named microRNAs (miRNAs) have important functions in lymphoma biology. In malignant B cells, miRNAs participate in pathways fundamental to B cell development, like B cell receptor (BCR) signalling, B cell migration/adhesion, cell-cell interactions in immune niches, and the production and class-switching of immunoglobulins. Normal B cells of a germinal center possess rearranged immunoglobulin heavy and light chain genes, and each isolated B cell possesses a unique IgH gene rearrangement. Since Burkitt lymphoma and other B-cell lymphomas are a clonal proliferative process, all tumor cells from one patient are supposed to possess identical IgH genes. When the DNA of tumor cells is analyzed using electrophoresis, a clonal band can be demonstrated, since identical IgH genes will move to the same position. On the contrary, when a normal or reactive lymph node is analyzed using the same technique, a smear rather than a distinct band will be seen. This technique is useful since sometimes benign reactive processes (e.g. infectious mononucleosis) and malignant lymphoma can be difficult to distinguish. The tumor consists of sheets of a monotonous (i.e., similar in size and morphology) population of medium-sized lymphoid cells with high proliferative and apoptotic activity. The 'starry sky' appearance seen under low power is due to scattered tingible body-laden macrophages (macrophages containing dead 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 amounts of basophilic cytoplasm with three to four small nucleoli. The cellular outline usually appears squared off.