Prognostic significance of immunhistochemical classification of diffuse large B cell lymphoma

Diffuse large B-cell Lymphoma (DLBCL) is heterogenous both clinically and morphologically. Because of this heterogenity, the different prognostic factors had been studied to be able to identify at diagnosis those patients who may benefit from more aggressive or experimental therapies. Currently, using a cDNA microarray, DLBCL can be divided into prognostically significant subgroups. Because this technology is expensive and not generally available, immunohistochemistry had been studied to subclassify DLBCL into prognostically significant groups. The aim of this study was to evaluate the use of immunoperoxidase staining for CD10, bcl-6, mum-1 and bcl-2 to subdivide DLBCL into prognostic subgroups and to examine the effect of this classification on overall survival rate (OS) and event free survival rate (EFS). Fifty consecutive patients with DLBCL diagnosed between January 1990 and May 2005 in our clinic were evaluated retrospectively. The M/F was 29/21 with the median age of 55,5 years. They were classified as germinal center B-cell-like (GCB) (30%), non- GCB (70%) [activated B-cell-like (ABC) (54%) and unclassified group (16%)] according to CD10, bcl-6, mum-1 and bcl-2 staining patern. The patient group mostly consisted of the patients with low and low-intermediate IPI (41 cases). IPI was found to be significantly predictive for OS and EFS (p=0.0001, p=0.01). The patients with low and low-intermediate IPI lived longer. When the protein expressions were studied individually, OS of the patients with CD10 positivity was found to be longer but OS of the patients with mum-1 positivity was found to be shorter. There were no significant effect of bcl-6 or bcl-2 on OS. The cases classified as GCB by immunohistochemistry had a significantly longer OS and EFS compatible with literature (p=0.002, p=0.04). In the literature, the 5-year OS for GCB group was 76%, compared with 34% for the non-GCB group (p=0.001) which was similar to that reported using the cDNA microarray. In our study, the 5-year OS for GCB group was 92%, compared with 40% for the non-GCB group (p=0.02). The existance of survival differences between GCB and non-GCB groups also in the patients with low IPI score showed the importance of prognostic classification in the riskadaptive treatment approaches. In conclusion, the classification as GCB and non-GCB phenotype based immunostains may enable to define more accurate prognostic groups in DLBCL.