3. The value of chromosome studies in the classification and management of the leukemias.

Chromosome identification techniques have shown the non-random nature of cytogenetic changes in leukemia. In addition, they have identified structural chromosome abnormalities occurring in specific types of acute leukemia as classified by the FAB criteria. Such cytogenetic sub groups are associated with differing prognoses. In acute lymphocytic leukemia, even the ploidy of the leukemic cells appears important in predicting prognosis. Identification of the Philadelphia (Ph1) chromosome has diagnostic significance in chronic granulocytic leukemia. This makes possible the classification of patients into Ph1 + and Ph1 - varieties which have different responses to therapy. Similar variations are found between the 2 groups of patients who do or do not develop additional abnormalities with blastic transformation. The implication of these findings in both acute and chronic leukemia may influence choice of therapy in the future.