Guidelines on Diagnosis and Treatment of Malignant Lymphomas

Burkitt Lymphoma/Leukaemia
Definition and Incidence
Burkitt lymphoma (BL) is an aggressive lymphoma, which
frequently presents at extranodal sites or as acute leukaemia.
The lymphoid proliferation is composed of monomorphic,
medium-sized B-cells with basophilic cytoplasm and numerous
mitotic figures. Translocation involving MYC is a constant genetic
feature and EBV is found in a variable proportion of cases. The
disease is rare with an incidence rate of < 0.2 / 100,000 / year
and sporadic BL accounts for 1-2% of lymphomas in Western
Europe and the USA. BL accounts for 30-50% of all childhood
lymphomas. The median adult age of onset is 30 years and the
male:female ratio is 2-3:1. Endemic BL occurs in equatorial
Africa and Papua New Guinea which corresponds to the
distribution of malaria and has a peak incidence in childhood (4 -
7 years). Immunodeficiency associated BL is primarily associated
with HIV infection and is often the AIDS – defining illness.
ICD – O Code:
9687/3 (lymphoma)
9826/3 (leukaemia)
Clinical Presentation
Patients with sporadic BL present with abdominal masses
frequently of the ileo-caecal region, a nasopharyngeal mass
or leukaemia. Other presentations include involvement of
the ovaries, kidneys and breasts. Retroperitoneal disease may
be associated with spinal epidural compression resulting in
paraplegia. Bone marrow involvement in a primarily
lymphomatous presentation is a poor prognostic feature and
is found in patients with a high tumour burden. Such patients
have a high LDH and uric acid levels and are at risk of the
tumour lysis syndrome.
Pathology
Classical BL is composed of medium sized cells, with round
nuclei, clumped chromatin and numerous nucleoli. The cytoplasm
is deeply basophilic and usually contains lipid vacuoles. There is a
high proliferation rate with numerous mitotic figures and “starry
sky” pattern due to the presence of numerous benign
macrophages which have ingested apoptotic tumour cells.
Immunophenotype
Tumour cells express membrane IgM with light chain restriction
and B-cell associated antigens such as CD 19, 20 and 22. CD10
and BCL6 are also expressed. The cells are negative for CD5,
CD23 and BCL2. A very high growth fraction is observed and
nearly 100% of cells are positive for Ki 67. Infiltrating T-cells are rare.
The blast cells of BL presenting as leukaemia have a mature
B-cell phenotype with surface Ig, light chain restriction and
expression of CD10, CD19, CD20, CD22 and CD79a, but not TdT.
Genetics
Burkitt lymphoma is defined by translocation of MYC at band q24
to chromosome 14 q32 (t(8;14)) or less commonly to light chain
loci at 2q11 or 22q11 leading to MYC over–expression. In
endemic cases the breakpoint on chromosome 14 involves the
heavy chain joining region (early B-cell) whereas in sporadic cases
the translocation involves the Ig switch region (later stage B-cell).
EBV genomes can be demonstrated in most endemic cases, 20-
40% of immunodeficiency BL and