Small non-cleaved cell lymphoma
Burkitt lymphoma is a rare form of malignant mature B-cell non-Hodgkin lymphoma.In Europe and north America it represents around half of all malignant non-Hodgkin lymphoma in children and around 2% in adults. Two incidence peaks occur: one in childhood/adolescence and the second after the age of 40 years. In Europe the standardized incidence ratio is 1/530,000 for individuals aged between 0 and 14 years and 1/670,000 for individuals aged between 15 and 19 years. Males are affected more than females.Patients with HIV in whom antiviral treatment is ineffective are particularly susceptible to Burkitt lymphoma. Two forms of the disease exist: an `endemic' form (sub tropical Africa) linked to the Epstein Barr virus (EBV) that presents classically in the form of a maxillary tumor (an abdominal tumor is often present, particularly in older children), and a `sporadic' form not linked to EBV that develops mainly in the abdomen. Burkitt lymphoma can also develop in the ear, nose and throat and more rarely in other locations (orbit, kidney, bone). The tumor is very proliferative and secondarily invades the bone marrow (in about 35% of cases) and the central nervous system (in about 15% of cases). It has the appearance of tumoral meningitis or paralysis of the cranial nerves. Burkitt leukemia, with the clinical characteristics of other types of leukemia, is possible. The tumors develop from the digestive tract (mainly the intestine) and extend to the peritoneum and sometimes also the liver, pancreas, spleen, kidneys or ovaries. The most frequent clinical signs are abdominal pain, nausea, an alteration of general state and/or the appearance of lymph nodes and tumors.In most cases Burkitt lymphoma is associated with a specific translocation t(8;14)(q24;q32) that juxtaposes the MYC/c-Myc gene (8q24) next to the heavy chain immunoglobulin gene (14q32). In rare cases the translocation affects chromosome 2 (kappa chain in immunoglobulins) or 22 (lambda chain in immunoglobulins). The cells express surface immunoglobulins and B differentiation markers (CD19, CD20). The proliferation index of the tumor is extremely high (Ki67 > 95%). EBV influences the genesis of the endemic form of Burkitt lymphoma but the mechanisms responsible are not well understood.Diagnosis is based on biopsy of a mass, an effusion puncture or bone marrow that reveals the presence of tumor cells. The extent of the tumor can be evaluated using images (mainly ultrasound and scanning).Differential diagnoses include other forms of abdominal tumors in children (Wilms tumor and neuroblastomas, although these are retroperitoneal, and desmoplastic tumors; see these terms) and other types of lymphoma and leukemia of B and T precursors in cases with bone marrow involvement.Management should be carried out in a specialist oncology/hematology centers. Treatment is with a few months of intensive chemotherapy. The efficacy of rituximab has not yet been proven but it is the subject of several clinical trials. Burkitt lymphoma constitutes a therapeutic emergency. The key to curing the disease is a combination of rapid and individualized management (particularly adapted to the frequent metabolic problems that occur at the start of treatment) and appropriate anti-tumor treatment.The current cure rate is in the order of 80-90% thanks to a difficult but relatively short treatment that is without long term sequelae.