ACUTE LYMPHOBLASTIC-LEUKEMIA WITH MATURATION - A NEW ENTITY WITH CLINICAL-SIGNIFICANCE

The diagnosis of 'ALL with maturation' (ALLm) is proposed. One hundred and one patients with untreated ALL were entered into this study. The diagnosis of ALLm was made when more than 20% of all nucleated elemen ts in the bone marrow showed maturation beyond prolymphocytes by light microscopic examination. The mature-appearing leukemic cells showed t he same immunophenotype to remaining lymphoblasts. The number of ALLm cases was 19(18.8%). The mean age at presentation of ALLm was 29 +/- 1 8, older than that of 18 +/- 16 of the remaining typical ALL (ALLt) (P =0.015). Remission was induced with daunorubicin, vincristine, prednis one and L-asparaginase. Only two of 19 ALLm patients achieved CR after 4 weeks induction chemotherapy. In contrast, 57 of 82 (69.5%) ALLt pa tients achieved CR after the same induction chemotherapy. There was no significant difference in immunophenotype of ALLm compared with ALLt. Labeling index of DNA topoisomerase ll alpha (TopoLl) was studied by immunohistochemistry. Initial TopoLl of ALLm (221 +/- 147) was much lo wer than that of ALLt (609 +/- 262, P=0.005). Furthermore, the remaini ng leukemic cells after chemotherapy were not labeled with anti-DNA to poisomerase ll alpha. The P53 protein was expressed in nine of 18 ALLm cases (50.0%) and P-glycoprotein was not expressed in ALLm cases. Twe lve of 19 ALLm cases were studied for carrying bcr/abl fusion by karyo typing and/or fluorescent in situ hybridization. Only two cases reveal ed bcr/abl fusion. In conclusion, ALLm is a separate entity of ALL whi ch has a very poor clinical course and is independent of other prognos tic factors. The morphologically mature leukemic cells are in resting GO phase.