ULTRASTRUCTURAL-LOCALIZATION OF MYELOPEROXIDASE ACTIVITY IN ACUTE MONOBLASTIC LEUKEMIA

In five patients with acute monoblastic leukemia (AMoL), the ultrastru ctural localization of myeloperoxidase (MPO) activity was investigated by two methods, one generally used for the detection of MPO and the o ther for the detection of platelet peroxidase. The MPO-positive rate a chieved was lower with the former method than with the latter, indicat ing that MPO is degraded during the fixation of AMoL cells for electro n microscopy. If the ultrastructural MPO positivity of leukemic cells varies when different detection methods are used, the possibility of m onocytic leukemia should be considered.