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 < 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.