Immunophenotyping in the diagnosis and classification of acute leukaemia.

Ninety-four consecutive patients with acute leukaemia were analysed using cytochemical stains and, in selected individuals, a panel of monoclonal antibodies combined with measurement of the enzyme terminal deoxynucleotidyl transferase. These results were correlated with the French-American-British morphological classification. Acute non-lymphoblastic leukaemia was diagnosed in 55 individuals on the basis of morphology and cytochemical criteria; 6 of this group were further studied with antibodies directed against specific myelomonocytic antigens, but no further clinically useful information was obtained. Blasts from 36 patients did not stain with either Sudan black or myeloperoxidase. These individuals were considered to have acute lymphoblastic leukaemia (ALL) and were further assessed with monoclonal antibodies directed against epitopes expressed on cells of lymphoid lineage; 10 were classified as arising from T precursors; 23 were of B lineage, of which 13 marked as common, 6 as null, 1 as pre-B, 2 as B-ALL and 1 to have a pattern characteristic of lymphoblastic lymphoma. Two cases could not be classified and 1 was found to have megakaryoblastic features. In a further 3 patients who had undergone lymphoblastic transformation as a terminal event in the course of chronic granulocytic leukaemia, 2 were immunophenotypically common and 1 was marked as a null cell. This study confirms the value of monoclonal antibodies for accurately assigning lineage to the acute leukaemias and particularly in those situations where conventional morphological criteria and cytochemical markers are inconclusive.