Diffuse large B-cell lymphoma in the young in Japan: a study by the Osaka Lymphoma Study Group.

Clinicopathological and immunophenotypical characteristics in 24 patients with diffuse large B-cell lymphoma (DLBCL) under 30 years of age in Osaka, Japan were examined, and the results compared to those of DLBCL patients aged over 40 years in Osaka and of young DLBCL patients in Western countries. The level of LDH and IPI score at initial diagnosis were significantly lower in young than older patients. The sex ratio (M:F) and age range (median) in the young and older groups were 1.18 and 11-30 (24.8) years and 1.59 and 42-87 (62.4) years, respectively. Extranodal presentation was higher in the young group (83.3% versus 60.0%, P < 0.05). Based on immunophenotyping with anti-CD10, bcl-6, and MUM1 antibodies, the cases were categorized as germinal center B-cell (GCB) (CD10+ or CD10-, bcl-6+, MUM1+) or non-GCB phenotype. The frequency of GCB type was significantly lower in the young group than older group (25% vs. 54%, P < 0.05), and much lower than that reported for young patients in Western countries. In situ hybridization revealed one of the young patients to be positive for Epstein-Barr virus (EBV). In the older group, none of 31 cases showed EBV positivity. Three year event-free and overall survival rates of young patients were better than those of the older patients, although not significantly different. DLBCL in the young in Japan is characterized by a much lower frequency of the GCB phenotype compared to that in Western countries.