Criteria for the Diagnosis of Acute Leukemia of Megakaryocyte Lineage (M7)

Excerpt

In the past, the French-American-British (FAB) Cooperative Group has classified acute myeloid leukemia on the basis of the morphologic features and number of blast cells, the percentage of maturing myeloid cells, and the percentage of the monocytic component in the bone marrow (1). We have previously considered peripheral blood findings only for the diagnosis of the M4 class of leukemia, that is, the monocytic component; in other forms of leukemia (types L1 to L3, M1 to M3, and M5 to M6), examination of the peripheral blood, though often important in arriving at a diagnosis, was not essential in the classification of the type of leukemia.

We have examined the peripheral blood films, bone marrow smears, and bone marrow biopsies of 16 well-documented cases of acute megakaryoblastic leukemia. In the diagnosis of megakaryoblastic leukemia, (known as M7), we depart from our previous procedure because, at times, bone marrow smears obtained by aspiration may not be adequate to make a diagnosis of acute leukemia or aspiration may fail due to increased bone marrow fibrosis. In these instances, the bone marrow cytologic findings cannot be used for classification, and peripheral blood films must be examined.