Myeloperoxidase-deficient polymorphonuclear leucocytes. (IV): Relation to FAB-classification in acute myeloid leukaemia.

In 148 consecutive cases of untreated acute myeloid leukaemia (AML) the relation between an increased number of myeloperoxidase (MPO)-deficient polymorphonuclear leucocytes (PMN) and a classification modified after the proposals outlined by the French-American-British Co-operative Group, the FAB classification, was investigated. In 22 cases with minimal granulocytic component, 8 M5, 13 M6, 1 M7, no one (0%) showed an increased number of MPO-deficient PMN. In 3 (13%) of 23 cases with slight granulocytic component, 3 M0, 20 M1, and in 49 (57%) of 86 cases with granulocytic differentiation (53 M2, 1 M3, 32 M4), an increased number was demonstrated. This difference was statistically significant at a high level (P less than 0.0001). The number of MPO-deficient PMN could not be estimated in 15 cases of AML and 2 additional cases were mixed leukaemias. It is concluded that an increased number of MPO-deficient PMN in acute leukaemia speaks in favour not only of AML, but suggests the diagnosis of subtypes with some granulocytic component, most likely M1, M2, M3 or M4. Furthermore, the results support the concept that in AML at least some of the mature myeloid cells may be involved in the leukaemic process.