Background: De novo CD5-positive diffuse large B-cell lymphoma (CD5 + DLBCL) is clinicopathologically and genetically distinct from CD5-negative (CD5-) DLBCL and mantle cell lymphoma. The aim of this retrospective study was to clarify the histopathological spectrum and obtain new information on the therapeutic implications of CD5+ DLBCL. Design and Methods: From 1984 to 2002, 120 patients with CD5+ DLBCL were selected from 13 collaborating institutes. We analyzed the relationship between their morphological features and long-term survival. The current series includes 101 patients described in our previous study. Results: Four morphological variants were identified: common (monomorphic) (n=91), giant cell-rich (n=13), polymorphic (n=14), and immunoblastic (n=2). Intravascular or sinusoidal infiltration was seen in 38% of the cases. BCL2 protein expression in CD5 + DLBCL was more frequent than in CD5- DLBCL (p=0.0003). Immunohistochemical analysis in 44 consecutive cases of CD5+ DLBCL revealed that 82% of these cases (36/44) were non-germinal center B-cell type DLBCL. The 5-year overall survival rate of the patients with CD5+ DLBCL was 38% after a median observation time of 81 months. Patients with the common variant showed a better prognosis than those with the other three variants (p=0.011), and this was confirmed on multivariate analysis. Overall, 16 patients (13%) developed central nervous system recurrence. Conclusions: Our study revealed the morphological spectrum of CD5+ DLBCL, found that the incidence of central nervous system recurrence in this form of lymphoma in high, confirmed that CD5+ DLBCL frequently expresses BCL2 protein and showed that it is mainly included in the non-germinal center B-cell type of DLBCL.
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