OBJECTIVE To study the clinicopathologic features and outcome of patients with diffuse large B-cell lymphoma (DLBCL), and to compare the differences between DLBCL of nodal and extranodal origins. METHODS One hundred and forty-two cases of de novo DLBCL collected during a 10-year period were reviewed. The clinicopathologic features and follow-up (2 - 108 months) data were analyzed. Tissue microarray blocks were performed and immunohistochemical studies using antibodies against CD10, bcl-6 and MUM1 were carried out. The cases were then further categorized into germinal center B cell-like (GCB) and non-GCB subtypes. RESULTS Primary gastrointestinal DLBCL often presented as early-stage disease (stage I or II) and was associated with low international prognostic index. They showed better prognosis than DLBCL of nodal and other extranodal origins. The positivity rates of CD10, bcl-6 and MUM1 were 19%, 51% and 58%, respectively. 36% of the cases belonged to GCB, while the remaining 64% were non-GCB. In general, DLBCL of extranodal origin showed more frequent bcl-6 expression than nodal DLBCL. As for extranodal DLBCL, GCB immunophenotype was often seen in thyroid and breast tumors, while testicular DLBCL usually carried a non-GCB immunophenotype. CONCLUSIONS DLBCL of various origins show a diversified GCB and non-GCB differentiation. Nodal and extranodal DLBCL, as well as extranodal DLBCL from different primary sites, carry different biologic characteristics and prognostic implications.