De novo CD5⁺ diffuse large B-cell lymphoma: A clinicopathologic study of 109 patients

De novo CD5⁺ diffuse large B-cell lymphoma (CD5⁺ DLBCL) is known to have phenotypically and genotypically different characteristics than CD5^- DLBCL and mantle cell lymphoma (MCL). To further characterize CD5⁺ DLBCL, 109 patients with CD5⁺ DLBCL were reviewed, and the results were compared with those of 384 CD5^- DLBCL and 128 cyclin D1⁺ MCL patients. Patients with CD5⁺ DLBCL showed a higher age distribution (median, 66 years; P = .0083) and a female predominance (male-female ratio, 49:60, P = .011) compared with those with CD5^- DLBCL. CD5⁺ DLBCL was more closely associated with many aggressive clinical features or parameters than CD5^- DLBCL: 69% older than 60 years (P = .039), 34% with performance status greater than 1 (P = .0016), 69% with serum lactate dehydrogenase level higher than normal (P < .0001), 62% with stage III/IV disease at diagnosis (P = .0023), 35% with more than one extranodal site (P = .023), and 40% with B symptoms (P = .0031). The overall International Prognostic Index score was thus significantly higher for the patients with CD5⁺ DLBCL than for those with CD5^- DLBCL (P = .00005). The most frequent site of extranodal involvement was bone marrow (28%), a higher frequency than that for CD5^- DLBCL (P < .0001) but lower than that for cyclin D1⁺ MCL (P = .0015). Histopathologically, CD5⁺ DLBCL showed centroblastic morphology except for 3 patients with immunoblastic disease, and interfollicular growth pattern (7%) and intravascular or intrasinusoidal infiltration (19%) were observed. Immunophenotypically, CD5⁺ DLBCL was characterized by a CD5⁺CD10^-CD19⁺ CD20⁺CD21^-CD23^- cyclin D1^- phenotype and a predominance of surface IgMκ. Of particular interest is that CD5⁺ DLBCL was characterized by a survival curve significantly inferior to that for patients with CD5^- DLBCL (P = .0026). These findings suggest that CD5⁺ DLBCL may constitute a unique subgroup of DLBCL.