We report a case of primary hepatic lymphoma (PHL) that developed in a patient with well controlled Sjogren's syndrome (SS) who had been receiving long-term prednisolone treatment. The tumor, found incidentally by ultrasonography, was shown as an extremely large, solitary liver mass that exhibited the immunohistological features of a B-cell lymphoma. An intensive regimen of chemotherapy induced complete regression of this mass. SS occasionally gives rise to lymphoma in salivary glands, however, there have been no previous reports of PHL in a patient with SS. This case study raises the possibility that SS itself, a form of autoimmune disease, and/or prednisolone-based immunosuppressive treatment for SS, predisposes to the occurrence of PHL. SS patients should be monitored vigilantly for the occurrence of extranodal lymphoma, including PHL, even if the SS is well controlled.