Abstract: Objective To investigate the clinicopathologic and immunophenotype of primary testis diffuse large B-cell lymphoma. Methods The clinical feature of 10 cases of primary testis diffuse large B-cell lymphoma was studied. The expression of CD10, Bcl-6, MUM1, Bcl-2 and Ki-67 was detected by immunohistochemitry on paraffin-embedded tissues. Germinal center B-cell like (GCB) or non-GCB immunophenotype was identified using an algorithm based on CD10, Bcl-6 and MUM1 expressions. ResultsThe mean age of these 10 patients were 65 years. Eight patients were at stage Ⅰ or Ⅱ. Six patients replaced or died within 5~42 months. The expression of CD10, Bcl-6, MUM1 and Bcl-2 was found to be 0, 50%, 70%, and 100%,respectively,in the 10 cases. Most cases (9/10) showed an expression pattern corresponded to the non-GCB immunophenotype. The Ki-67 index indicated a relatively high proliferation of the lymphoma cells with a mean 70%. ConclusionPrimary testis large B-cell lymphoma shows non-GCB immunophenotype. This feature adding with high Bcl-2 expression and Ki-67 index might be associated with its poor prognosis.