The clinical usefulness of tumor markers for malignant lymphoma is thought to be in monitoring the therapeutic effect and as a prognostic factor before treatment. The former include specific biological marker such as soluble interleukin-2 receptor measured by ELISA. The latter are cellular prognostic markers detected by immunohistological and flow cytometric analysis. The cyclin D1 over-expression of mantle cell lymphoma in diffuse large B-cell lymphoma, which should be recommended for myeloablative therapy, is a significantly poor prognostic risk factor.