Most relapses of diffuse large B-cell lymphoma (DLBCL) occur as high-grade lymphoma within the first two years after diagnosis. Relapses as indolent lymphoma are rare events, and the true incidence of this phenomenon is unknown, since literature data are scarce/ and usually restricted to case reports. Analogously, reported treatment strategies are rather heterogeneous, since no standard of care is established and advanced age together with previous anthracycline exposure may narrow the therapeutic choice. The goal of this observational study is to assess epidemiological, clinical characteristics and survival of diffuse large b-cell lymphoma (DLBCL) relapsing as indolent lymphoma. More precisely, the study aims at identifying diagnostic and imaging features associated with relapse as indolent lymphoma and at evaluating disease response to selected therapies.