To our knowledge, this is the first study examining CD5 expression as a prognostic and predictive biomarker for outcomes of R-based immunochemotherapy in MZL. CD5+ MZL was characterized by disseminated presentation with universal peripheral blood involvement, but after adjustment for other factors, CD5 expression was not independently prognostic. However, we observed worse response rates, PFS, and OS for CD5+ MZL treated with first-line R monotherapy, but not among those treated with BR, suggesting that the BR combination might be preferable in this subgroup.