The expression of Bcl-2 by proliferating cells varies in different categories of B-cell lymphoma

The expression of Bcl-2 by proliferating cells varies in different categories of B-cell lymphoma Aims: To investigate the relationship between Bcl-2 protein expression and cell proliferation at single-cell level in B-cell lymphomas using double-labelling techniques. Methods and results: The relationship between Bcl-2 protein expression and cell proliferation was explored in 124 cases of B-cell lymphoma using double immunofluorescence labelling for Bcl-2 and Ki67. In follicular lymphoma, marginal zone lymphoma and a subset of chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL), neoplastic cells tended to lose Bcl-2 when they are in cell cycle. This pattern is usually maintained in both follicular lymphoma and CLL/SLL when they undergo high-grade transformation. In mantle cell lymphoma, diffuse large B-cell lymphoma and a subset of CLL/SLL, the inverse relationship (between Bcl-2 and Ki67) was not observed, i.e. the proliferating cells tended to show co-expression of Bcl-2. Conclusions: In low-grade lymphomas, including those that are transformed, Bcl-2 expression is lost when cell proliferate. However, in more aggressive tumours (i.e. mantle cell and de novo diffuse large B-cell lymphomas) the inverse Bcl-2/Ki67 relationship was not observed. It would be of interest to explore the clinical implications in lymphoma of the presence and absence of the inverse Bcl-2/Ki67 pattern.