Terminal deoxynucleotidyl transferase in various immunophenotypic cells in leukemia]

The staining results of terminal deoxynucleotidyl transferase (TdT) in leukemic cells of peripheral blood or bone marrow in 55 patients showed that 22 (40%) patients were found positive for TdT staining: 17 patients with acute lymphoblastic leukemia (ALL), 2 acute non-lymphocytic leukemia (ANLL) and 3 hybrid acute leukemia (HAL). The positive rate of ALL (17/21) was significantly higher than that of ANLL (2/21, P < 0.005). The leukemic cells of HLA-DR+CD19+TdT- were demonstrated to express some of myeloid restricted antigens (HI98, HIM 4, HIM 5) (3/3), which suggested that these cases were leukemias of myeloid origin. None of the 8 patients with M 0/M 1 ANLL was positively stained for the enzyme. Our results showed that TdT detection is of great value in the diagnosis and differentiation of both poorly differentiated and hybrid acute leukemia.