The bcl-2 oncogene in Hodgkin's disease arising in the setting of follicular non-Hodgkin's lymphoma

Expression of the bcl-2 proto-oncogene on chromosome 18 is deregulated by the 14; 18 chromosomal translocation, an abnormality that is consistently associated with follicular non-Hodgkin's lymphomas (NHL). Because bcl-2 is believed to function by prolonging cell survival rather than by increasing proliferation, the presence of t(14; 18) in Hodgkin's disease (HD) would have profound implications for the pathogenesis of this neoplasm. We evaluated 32 cases of HD for t(14; 18) by polymerase chain reaction (PCR). These results were correlated with expression of bcl-2 oncogenic protein by Hodgkin cells and with the presence of Epstein-Barr virus (EBV), as determined by immunohistochemistry or in situ hybridization. PCR provided evidence of t(14; 18) in only 2 HD cases (6%), both of which were associated with a prior history of follicular lymphoma, and both of which were among the 7 cases (22%) with strong bcl-2 expression in Hodgkin cells. In at least 1 of the cases, the translocation involved identical chromosomal breakpoints in both types of lymphoma. Furthermore, 7 additional cases of combined follicular NHL and HD showed strong bcl-2 staining in Hodgkin cells. Although EBV was detected in 6 of 30 cases, it was not associated with t(14; 18) and usually not with strong bcl-2 expression. These results suggest that a small proportion of HD cases might evolve from follicular NHL, possibly through molecular events superimposed on the t(14; 18). High-level bcl-2 expression in Hodgkin cells is a potentially useful but not definitive marker for these cases.