Reduced apoptotic cell death in follicular lymphoma.

It has been hypothesized that inhibition of germinal centre cell apoptosis may underlie the development of follicle centre cell lymphomas. We have performed a comparative, quantitative study of apoptotic cell death in germinal centres and in the neoplastic follicles of centroblastic-centrocytic, follicular, non-Hodgkin's lymphoma (Cb/Cc NHL). Ten cases each of reactive follicular hyperplasia and Cb/Cc NHL were analysed. One-micrometre-thick resin-embedded sections were examined at x 1000 magnification. The total numbers of cells, nuclear containing apoptotic bodies, and mitoses were counted in each follicle and the apoptotic and mitotic indices were derived. Transmission electron microscopy was performed on selected cases to confirm the typical features of apoptosis. The mean apoptotic (4.9 per cent) and mitotic indices (0.9 per cent) for the germinal centres were significantly higher (P much less than 0.001) than those for the neoplastic follicles (0.9 and 0.14 per cent). These results lend support to the recent proposal that reduced apoptotic cell death may be important in the pathogenesis of follicular lymphomas.