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DEFINITION AND EPIDEMIOLOGY

  • Burkitt lymphoma (BL) may present in three distinct forms: endemic (African), sporadic, and immunodeficiency-associated.

  • The endemic form is found in eastern equatorial Africa, with a peak age incidence at 4 to 7 years, and it is nearly twice as frequent in boys as in girls.

  • Sporadic BL, defined as cases outside of endemic African regions, accounts for 1% to 2% of all patients with non-Hodgkin lymphoma (NHL).

  • The incidence is higher in males than in females, and the median age of onset is 30 years.

  • Immunosuppression-related BL increased in incidence during the AIDS epidemic.

PATHOPHYSIOLOGY

  • The unifying feature of all three types of BL is activation of the c-MYC gene, typically resulting from translocations involving the long arm of chromosome 8, which carries c-MYC.

    — Such translocations commonly also involve the long arm of chromosome 14, which carries the immunoglobulin heavy chain gene complex, but might instead involve chromosome 2 or 22, which carries the immunoglobulin kappa or lambda light chain gene complex, respectively.

  • Translocations are thought to occur via double-strand breaks that occur during the normal B-cell class-switch reaction and somatic hypermutation.

  • Up to one-third of cases also might have alterations involving the short arm of chromosome 17 at 17p13.1, involving the TP53 gene encoding p53. Loss of p53 function might be selected in BL cells that otherwise would be induced to undergo apoptosis in response to overexpression of cMYC

  • BL has a highly characteristic gene expression profile (GEP), with high expression of MYC-dependent genes as well as markers of germinal center B cells and relatively low expression of target genes of the nuclear factor-κB pathway. The GEP is able to distinguish BL from diffuse large B-cell lymphoma (DLBCL) with a c-MYC translocation.

  • Next-generation sequencing has found that mutations in ID3, TCF3, and CCND3 occur frequently.

  • Evidence of Epstein-Barr virus (EBV) is found in essentially all patients with African BL, 30% to 40% of patients with immunosuppression-associated BL, and 20% of patients with the nonendemic form of disease.

HISTOPATHOLOGY

  • A diffuse monomorphic population of medium-sized cells with round nuclei, multiple nucleoli, and basophilic cytoplasm effaces normal nodal architecture (Figure 65–1, A and B). A high rate of spontaneous apoptosis leads to the characteristic “starry sky” appearance (Figure 65–1A).

  • BL cells are mature B cells that typically express CD19, CD20, CD22, CD79a, BCL6, BCL10, and surface IgM. BL cells lack expression of CD5 or CD23, Mum-1, and terminal deoxynucleotidyl transferase (TdT).

FIGURE 65–1

A. Lymph node biopsy section. A monomorphic population of Burkitt lymphoma (BL) cells interspersed with macrophages engorged with cellular debris as a result of the high cell turnover rate (high rate of apoptosis and cell proliferation). These “tangible body macrophages,” a term derived from a description of phagocytized nuclear debris of small lymphocytes by macrophages in germinal centers ...

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