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Highly aggressive lymphomas are relatively uncommon in adults, comprising approximately 4% to 5% of all non-Hodgkin lymphomas in the United States and Western Europe. The designation of "highly aggressive" is generally restricted to precursor T-cell and B-cell lymphoblastic lymphoma/leukemia and Burkitt's lymphoma/leukemia. Treatment strategies for lymphoblastic lymphoma and Burkitt's lymphoma include complex, highly intensive combination chemotherapy regimens, which may be curative. As with other subtypes of NHL, emerging data from gene-expression profiling and related techniques are helping to define these entities more precisely and identify potential new rational therapeutic targets.

A human lymphoma cell line, positive for the Epstein-Barr virus (EBV)-associated nuclear antigen, was recently established from a North American Burkitt's lymphoma. This cell line, SU-AmB-2, contained EBV DNA both in the form of circular, nonintegrated DNA molecules of viral genome length, present in multiple copies per cell, and as integrated sequences. Having DNA present in both of these forms, it resembled cell lines established from African Burkitt's lymphomas. In studies on EBV strain differences, the episomal viral DNA in Burkitt's lymphoma cells may now be compared with viral DNA in nonmalignant cells with the use of cell lines from Burkitt's lymphoma patients of similar geographic origin.

Twenty American patients with Burkitt's lymphoma (BL) were studied serologically and biochemically to detect an association with Epstein-Barr virus (EBV). A wide range of antibody reactivities was encountered. Five patients had serological profiles similar to those of African patients with BL: one and possibly two of these patients harbored EBV-DNA in their tumors. Fifteen patients had low or absent antibody to EBV: tumors from 10 of these patients lacked evidence of EBV-DNA. An unexplained association between elevated antibody (greater than or equal to 1:80) to EBV virus capsid antigen (VCA) and a favorable prognosis was noted in this series; this prognostic observation requires further substantiation. Thus, it appears that EBV-associated BL is inversely proportional to tumor endemicity. An etiological role for EBV in BL remains speculative.