CD99 expression and newly diagnosed diffuse large B-cell lymphoma treated with rituximab-CHOP immunochemotherapy.

In order to evaluate prognostic value of CD99 expression in patients with diffuse large B-cell lymphoma (DLBCL) who underwent treatment with rituximab-CHOP immunochemotherapy, immunohistochemistry for CD99/CD10/BCL-2/BCL-6/MUM-1 was performed on nodal DLBCL specimens from 70 patients. Patients were classified as either germinal center B-cell (GCB) subtype or non-GCB subtype according to the Muris algorithm. A superior 2-year event-free survival (EFS) was observed in patients with the GCB subgroup, compared to those with the non-GCB subgroup (p = 0.034). The distribution of CD99 expression (29 patients; 41.4 %) did not show deviation according to subtype and was not prognostic for survival in the entire patient population. Among patients with the GCB subgroup, better EFS and overall survival (OS) were observed in CD99+ patients, compared to CD99- patients. Conversely, among patients with the non-GCB subgroup, inferior EFS and OS were reported in CD99+ patients. Superior 2-year EFS (p = 0.004) and 2-year OS (p = 0.003) were observed in patients with GCB/CD99+ and non-GCB/CD99- compared to the others, and the combination classification was found to be an independent prognostic factor.