Coexpression of Bcl-6 and CD10 in diffuse large B-cell lymphomas: Significance of Bcl-6 expression patterns in identifying germinal center B-cell lymphoma

Most follicular lymphomas (FLs) transform to diffuse lymphoma eventually, c omprising a significant proportion of diffuse large B-cell lymphoma (DLBCL) . judging by bcl-2 rearrangement (bcl-2R), one third of DLBCLs are believed to be of FL derivation in the Western population. However, bcl-2R is not s pecific and is not detectable in every case of FL. In East Asia, FL is unco mmon but DLBCL is not. The proportion of tumors of FL origin in DLBCL is no t known in this region. The coexpression of Bcl-6 and CD10 proteins, a reli able marker to identify germinal center (GC) B-cell lymphoma including FL, was analyzed in primary nodal DLBCLs (n = 104) diagnosed at major hospitals in Seoul during a recent 2-year period, along with well-defined cases (n = 17) of nodal FL as controls. Bcl-2 protein expression (n = 77) was also st udied along with bcl-2R (n = 64), by polymerase chain reaction. Formalin-fi xed archival specimens were used in all these assays. The Bcl-6/CDIO coexpr ession was observed in 35 DLBCLs (34%) and 14 FLs (82%), and most of them s howed a pattern of Bcl-6 expression similar to that of the GC. Bcl-2 expres sion or bcl-2R did not correlate with Bcl-6/CD10 coexpression. Histological ly, compartmentalizing sclerosis was associated with a high rate of the coe xpression (8 of 10). In conclusion, to detect GC B-cell lymphoma in routine biopsy specimens, a pattern of Bcl-6 staining similar to the GC must be id entified. Bcl-6(+)/CD10(+) GC B-cell lymphomas thus defined comprised one t hird of primary nodal DLBCLS in Korea. The incidence rate is similar to tha t in the West. The reasons for the discrepancy between the incidence of GC B-cell lymphoma. and the paucity of the follicular pattern in East Asian su bjects warrant further studies. Copyright (C) 2001 by W.B. Saunders Company .