071 Cut - off Value Determination for Prognostic Markers in Diffuse Large B - Cell Lymphoma ( Dlbcl )

Splenic marginal zone B-cell lymphoma (SMZL) is an indolent lymphoma showing some characteristic cyto-histological, cytogenetical and molecular features. Phenotypically it is defined by a negative profile with no CD5, CD10, CD23, CD43 expression. A CD5 positivity has been reported in some typical MZL cases and proposed as a marker for a more aggressive and disseminated disease. The differential diagnosis between CD5+ SMZL and B-CLL or MCL is still controversial in peripheral blood without histological control. Here we compared a series of 35 CD5 positive SMZL histologically proven in 26 cases and without t(11;14) detected by FISH, with 44 typical CD5 negative SMZL. From a clinical, cytological and immunological point of view, the CD5+ SMZL presented many similarities with the CD5SMZL. The main differences consisted in a higher lymphocytosis at diagnosis (7,9 G/L in CD5+ cases and 3,9 G/L in CD5cases, respectively p=0.0006) and a more frequent IgM isotype of the monoclonal component (76% vs 59%). No CD5 negative B-cells were detected in spleen specimen and the tumoral mass assessed by spleen weight seemed similar between both groups. These data suggest that CD5 expression gives B-cells a higher propensity to recirculate from spleen. Karyotypic changes were similar in both groups and included the chromosomal abnormalities previously described in SMZL. However, the trisomy 18 was more frequent in the CD5+ group (29%) than in the CD5group (11%). Most CD5+cases were mutated in contrast to the CD5cases (86% vs 54%; p=0.024). The usage of VH4 was more represented in the CD5+ cases (5/21; 24%) than in the CD5cases (2/24; 8%) No difference in outcome and overall survival was found between both groups. In conclusion, this study allowed to confirm the existence of CD5 positive SMZL (25% of our SMZL series), closely related to classical CD5SMZL and distinct from CLL and MCL. The differences observed with CD5cases, especially the VH usage, suggest that this entity may arise from a distinct cell in the marginal compartment.