TdT

Background

Terminal deoxynucleotidyl transferase (TdT) is an unusual deoxynucleotide polymerizing enzyme with a molecular weight of about 58 kDa found normally only in B- and T-cell lymphoblasts/prelymphocytes. TDT is widely used as a marker of lymphoblastic leukemia and is strongly expressed in acute lymphoblastic leukemia/lymphoblastic lymphoma. Immunohistochemical detection of TdT has value in classification of malignant lymphomas and acute leukaemias, particularly for the identification of pre-B and pre-T acute lymphoblastic leukemia/lymphoblastic lymphoma.