OBJECTIVE: Expression of CD44 variant (v) isoforms substantiates poor prognosis in patients with hematological malignancies. We have previously shown that CD44v6 expression in diffuse large B-cell lymphoma (DLBCL) correlates with advanced disease stage and is predominantly detected in non-germinal center (GC) B-cell like DLBCL subtypes. With the growing number of associated molecules found to form functional complexes with CD44, we analyzed a larger cohort of cyclophosphamide, doxorubicin, vincristine, prednisone- (CHOP) and equivalently treated DLBCL patients to define the prognostic role of such CD44-associated molecules. PATIENTS & METHODS: 290 formalin-fixed, paraffin-embedded primary DLBCL tissue samples were analyzed in tissue microarrays. To obtain potential biologically-meaningful associations, optimal cut-off values were established by receiver operating characteristic (ROC)-curves. The prognostic significance of every possible multimarker phenotype was also addressed. RESULTS: We showed that co-expression of any of the CD44v with the receptor for hyaluronic acid-mediated motility (RHAMM, CD168) identifies a subgroup of DLBCL patients with a very poor prognosis, independent of the international prognostic index. These patients did not show C-MYC translocations or amplifications. CD44v-RHAMM co-expression was most prevalent in non-GC DLBCL cases and usually coincided with expression of osteopontin (OPN). CONCLUSION: Evaluation of CD44v-RHAMM co-expression may improve the accuracy of DLBCL prognosis and identify a subgroup of patients, who will benefit from therapeutic alternatives to CHOP.