Diagnosis of Burkitt Lymphoma/Leukaemia

Morphology - A reasonable guide in blood, bone marrow and on imprints but poor in HE sections.

Immunophenotype - Much more specific but can be variable and cannot be absolutely relied on. Usually cells are CD19, 20 and 22 positive, CD23 negative, surface immunoglobulin positive (this is usually strong with both IgM and IgD on the cell surface). There is light chain restriction. CD10 positive, 38 positive. Ki 67 > 95%. There may be absence of BCL6 expression. BCL2 expression may be increased.

Cytogenetics/FISH - t8:14, t2:8, t8:22, t14:18 C-Myc rearrangement.

Unresolved issues

• H&E appearances are poorly reproducible. “L3” appearances can be seen in other conditions and may not be seen in patients who otherwise appear to have Burkitt’s lymphoma/leukaemia.
• C-Myc rearrangements are “always” seen in Burkitt lymphoma but may be seen in non-Burkitt lymphoma.
• What does 14:18 mean, what is its relation to BCL2 expression for example?
• One rarely gets a “full house” of the characteristic features listed above and thus one may have to decide where an atypical case best fits – DLBCL or BL. (See Cogliatti et al).

Comment

• LY10 addressed these issues. It was designed for both high and low risk patients, the former included patients with blood, bone marrow and CNS involvement.
• Entry to LY10 required – diffuse B cell lymphoma withCD20+, CD79+; and 100% Ki67 expression.

It is important to focus closely on Ki67 and several slides from different parts of the tumour may be required. It is recommended that the haematologist involved looks at the Ki67 slides with the histopathologist as soon as possible.

Ki67 is an intra-nuclear antigen and is not easily amenable to flow cytometry.

For further information , see Cogliatti et al BJH (2006) 134: 294-301 and LY10 protocol 2002 – this gives a good review of diagnostic problems in BL.