Primary gastric diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease entity that includes patients with (DLBCL/MALT) and without detectable mucosa-associated lymphoid tissue (MALT) lymphoma components (de novo DLBCL). We sought to evaluate the clinical characteristics and outcome of this disease in a large number of cases. Patients with primary gastric DLBCL (n=162) seen on 2001-2011 at the Tianjin Medical University Cancer Institute and Hospital and the First affiliated Hospital of Chinese PLA General Hospital were retrospectively reviewed. The distribution of sex, age, Lugano staging, and other main clinical characteristics was similar between the de novo DLBCL and DLBCL/MALT groups (p>0.05). However, the proportion of patients with a stage-modified international prognostic index (m-IPI) ≥ 2 was higher in the de novo DLBCL (34 %) than the DLBCL/MALT group (17 %) (p=0.026). In addition, the Helicobacter pylori infection rates were higher in the DLBCL/MALT (75 %) than the de novo DLBCL group (36 %) (p<0.001). Five-year progression-free survival (PFS) and overall survival (OS) estimates were similar for patients in the de novo DLBCL (p=0.705) and DLBCL/MALT groups (p=0.846). Surgical treatment did not offer survival benefits when compared with chemotherapy for 5-year PFS (p=0.607) and OS estimates (p=0.554). There were no significant differences in 5-year PFS and OS estimates for patients treated with rituximab-chemotherapy (p=0.261) or conventional chemotherapy (p=0.227). Non-GCB subtype and m-IPI ≥ 2 were independently associated with shorter OS, and advanced stages of lymphoma were independently associated with shorter PFS.