Mature T Cell Leukemias

Abstract

Abstract The mature T cell leukemias are clonal proliferations of differentiated T lymphocytes that demonstrate the phenotype of mature, peripheral (nonthymic) T cells of helper or suppressor cell type. Mature T cell leukemias, in contrast to T cell acute lymphocytic leukemias, are negative for terminal deoxynucleotidyl transferase. Monoclonality of the lymphocytes in the mature T cell leukemias has been shown by demonstration of clonal rearrangement of the T cell receptor gene (Aisenberg et al, 1985). Morphologically related leukemias may demonstrate a natural killer (NK) cell phenotype. NK cells share expression of some T cell antigens (CD2, CD8) but lack the T cell receptor and T cell receptor gene rearrangement. The French-American-British Cooperative Group classification of chronic (mature) lymphoid leukemias recognizes four categories of chronic T cell leukemia: (1) large granular lymphocyte leukemia (formerly considered T cell chronic lymphocytic leukemia); (2) T-prolymphocytic leukemia; (3) adult T cell leukemia-lymphoma; and (4) Sezary’s syndrome (Bennett et al, 1989). T cell chronic lymphocytic leukemia is now considered a disorder closely related to (if not identical with) T cell prolymphocytic leukemia and is distinguished from large granular lymphocyte leukemia. Large granular lymphocyte leukemia may be of either T cell or NK cell phenotype. T cell chronic lymphocytic leukemia and T cell prolymphocytic leukemia are clonal proliferations of phenotypically mature T cells involving the peripheral blood and bone marrow.