A 78-year-old woman suffered from superior vena cava (SVC) syndrome. Computed tomography and angiography revealed a mass within the SVC. The SVC was resected via median sternotomy, followed by reconstruction using an artificial graft. The resected specimen showed a polypoid tumor within the SVC that had invaded the wall of the SVC. Histologic diagnosis was diffuse large-cell non-Hodgkin's lymphoma. Most surrounding lymph nodes showed reactive swelling, but one showed a partial microscopic metastasis. These pathologic findings indicated that the tumor was an SVC-originating malignant lymphoma. The patient is now alive and tumor-free 65 months after the operation.