Recent advances in the cutaneous T cell lymphomas.

Classical mycosis fungoides and Sezary syndrome are part of a larger spectrum of cutaneous T cell lymphomas. Widespread infiltration of the skin, early invovlement of the T cell regions of lymphoid tissue and relative sparing of the bone marrow apparently result from the distinctive properties of the neoplastic lymphocytes. Clinically relevant suppression of normal T cell function has been noted in each patient in the leukemic phase and probably results from both dilution in the blood and lymphoid tissues of normal T cells and production of macrophage inhibitory factor(s) by the neoplastic cells. The abnormal T cells, which in these malignancies appear to be derived from normal "helper" T cells, which facilitate immunoglobulin production by normal B cells. Leukapheresis effectively reduces the tumor load and associated morbidity in selected patients but alone does not prevent the evolution to rapidly proliferating lymphomas. The basis of the remarkable affinity for the skin and identification of the primary site of proliferation and differentiation of the malignant T cells of these processes are important but, as yet, unresolved questions.