Cytochemistry of the acute leukaemias.

The use of the Romanowsky staining technique, Sudan Black B, the periodic acid-Schiff reaction and methods for revealing peroxidase, acid and alkaline phosphatases and butyrate, acetate or chloroacetate esterases for identifying and discriminating subvarieties of acute leukaemia at the light microscope level is reviewed and the results of their application in a recent study of the first 720 cases admitted to the Medical Research Council's 8th Acute Myeloid Leukaemia trial summarized. The distribution of varieties of acute myeloid leukaemia and the relevance of age and cytochemical findings to clinical prognosis is presented. Identification of the predominant primitive cell - myeloblast, promyelocyte, monoblast, and others - appears to have little prognostic significance. In fact, the presence of periodic acid-Schiff positive erythroblasts is a bad prognostic sign. The association of certain cytochemical findings with the 15;17 translocation and acute promyelocytic leukaemia, especially the patterns of esterase positivity in Auer rods and the Sudan Black, peroxidase, periodic acid-Schiff and esterase findings characteristic of the 8;21 translocation are illustrated. Cytochemical features helpful in distinguishing acute megakaryoblastic leukaemia, notably the periodic acid-Schiff reaction, differential esterase reactivities and 5'-nucleotidase, are discussed and illustrated. Brief reference is made to the cytochemical differentiation of lymphoblastic leukaemias. Details of a technical method for the demonstration of 5'-nucleotidase are given.