To investigate the specificity and sensitivity of Oct2 protein expression in lymphoma cells and its significance in diagnosis and classification of lymphoma.Formalin-fixed and paraffin-embedded materials from 129 cases of lymphoma and 10 cases of reactive lymphoid hyperplasia (RLH) were studied by EnVision immunohistochemistry for Oct2 protein.Oct2 was mainly expressed in germinal center cells of RLH. It was diffusely expressed in B-cell lymphoma cells. 97.7% cases (85/87) of B-cell lymphoma and 3.8% cases (1/26) of T-cell lymphoma were positive for Oct2 protein. In comparison, the expression rates for CD20 and CD79alpha in B-cell lymphomas were 90.8% (79/87) and 84.7% (61/72) respectively. The difference in expression rates between Oct2 protein and CD20 was not statistically significant (P > 0.05) There was, however, significant difference in expression rates between Oct2 protein and CD79alpha (P 0.05).As a relatively sensitive and specific marker for B cells, Oct2 can serve as a useful antibody for the diagnosis and differential diagnosis of lymphoma.