Burkitt lymphoma is a highly aggressive lymphoma of mature B cells. In the majority of patients, it is an extra-nodal lymphoma but some patients have leukaemic manifestations. Three variants are recognized on the basis of epidemiological and clinicopathological features – endemic, sporadic and human immunodeficiency virus (HIV)-related [1,2]. Endemic Burkitt lymphoma occurs in equatorial Africa and in Papua New Guinea where malaria is hyperendemic, is strongly related to Epstein–Barr virus (EBV) infection, occurs in children and usually affects the jaw bones and orbit. Sporadic cases occur in developed countries, are related to EBV in only about 25% of cases, occur in children and young adults and most often affect the gastrointestinal tract although, as with the endemic type there may be involvement of the ovaries, kidney or breast. Breast involvement is often associated with the onset of puberty, pregnancy or lactation and is frequently massive and bilateral. HIV-related Burkitt lymphoma is associated with EBV in about one-third of cases and often presents with disseminated disease, for example involving lymph nodes and bone marrow. Patients with X-linked lymphoproliferative disease are at increased risk of developing Burkitt lymphoma.
This lymphoma is derived from a germinal centre B cell without somatic hypermutation. Gene expression analysis has produced evidence that Burkitt lymphoma and a subset of diffuse large B-cell lymphoma are much more closely related than had previously been realized [3,4]. In addition to cases of de novo Burkitt lymphoma, there are cases that represent transformation of a pre-existing low-grade lymphoma.
Clinical features vary according to whether the disease is endemic, sporadic or HIV-related. The tumours are remarkable for their high rate of growth, as a result of which patients often present with bulky, locally advanced disease. Central nervous system (CNS) and bone marrow involvement are common and lymphadenopathy and leukaemia occur in a minority of patients. A pure leukaemic form, the Burkitt leukaemia variant, with exclusive peripheral blood and bone marrow involvement is rare .
Haematological and pathological features
In patients with peripheral blood and bone marrow involvement, the lymphoma cells have the features described by the French–American–British (FAB) group as L3 acute lymphoblastic leukaemia (ALL). However, it should be noted that this condition is correctly classified as a lymphoma (as in the WHO classification), not as ALL, since the cells are mature B cells. Neoplastic cells are medium sized with strongly basophilic, vacuolated cytoplasm (Figures 13.1 and 13.2). The vacuoles contain lipid and stain with Oil Red O. The same cytological features are apparent in films from fine needle aspirates and in imprints from tissue sections (Figure 13.3).
Peripheral blood film in Burkitt lymphoma showing two cells with strongly basophilic vacuolated cytoplasm. Romanowsky stain, ×100 objective.