“…High TdT levels have been found in the normal thy mus [6,19] and a trace of enzyme activity has been detected in cells from normal bone marrow [1,6,10,14]. Increased TdT activ ity has been reported to be present in almost all cases of ALL [3,5,6,10,13,14,16,19,20], as well as in a number of cases of chronic myelocytic leukemia (CML) in biastic crisis [3,5,6,13,14,17,19,23,24], in lym phoblastic lymphoma [7,16] and in rare cases of acute myelocytic leukemia (AML) [3,25],…”