S-100 beta positive T cell leukemia.

We reported a peculiar case with T cell leukemia. The patient was a 34-year-old woman showing extensive splenomegaly and marked leukemic cell proliferation and running a rapid fatal clinical course. The leukemic cells were morphologically ordinary lymphocytes showing suppressor/cytotoxic(s/c) T cell phenotypes and containing S-100b protein. Southern blot analysis revealed rearrangement of the beta chain genes of the T cell receptor (TcR) of the leukemic cells. Because these phenotypic and morphologic features were identical with those of S-100 beta+T lymphocytes (S-100 beta +TL) in normal human peripheral blood, we regarded this case as S-100 beta +T cell leukemia. We discussed clinicopathological features of S-100 beta +T cell leukemia/lymphoma by assessing similar cases reported so far. S-100 beta +T cell leukemia/lymphoma is a new type of s/c T lymphocytic leukemia/lymphoma with aggressive features.