Studies on aminopeptidase activity in acute non-lymphocytic leukemia. The relation to peroxidase reaction

Aminopeptidase (AMP) activity of leukemic cells in acute non-lymphocytic leukemia (36 cases) was examined by comparing peroxidase (PO) activity. The examination of AMP activity was useful for the diagnosis of non-lymphocytic leukemia in 19 of 36 cases rather than PO activity. Especially in acute monocytic leukemia its tendency was conspicuous. Furthermore, in 5 cases AMP was positive whereas there was no evidence of PO activity. On the contrary, PO was evident in 11 cases. The cases which revealed the same degree of both activities were only 4 and in 2 cases they were completely negative. Although the total number of PO negative cases was 7, ultrastructural endogenous myeloperoxidase reaction was clearly observed in granules of leukemic cells in all cases examined (6 cases). The diagnosis and classification of leukemia must be made using several techniques, and especially in non-lymphocytic leukemia cases, not only PO activity but also the examination of AMP activity is important. Therefore, one must be prudent in applying the FAB classification in acute leukemia.