Radically new research.

-Terminal deoxynucleotidyl transferase (TdT) was estimated in the tissues of 42 patients with lymphoma, whose cells were also typed by the use of surface markers. Four of the 8 patients with T-cell lymphoma were TdT+ including patients whose lymph nodes showed an undifferentiated or poorly differentiated appearance. The TdTT-cell lymphomas included cases with diffuse histiocytic, Sezary cell, diffuse, poorly differentiated and angio-immunoblastic histology. The tissues of 31 patients with B-cell lymphoma were invariably TdT-, whether the histology was poorly differentiated, well differentiated, nodular, diffuse, histiocytic or Burkitt type, and including cases with about equal proportions of T and B cells, and those whose cells showed non-capping and capping surface immunoglobulin. Hodgkin's tissue was also invariably TdT-. We conclude that estimation of TdT in tissues of patients with malignant lymphoma may be a useful test in diagnosing the T-cell lymphoma, particularly in patients with tumours of undifferentiated or poorly differentiated histology.