ABSTRACT
I. INTRODUCTION In the recent past, most chronic leukemias were diagnosed under the rubric of chronic lymphocytic leukemia (CLL) if blast cells were not a feature and the neoplastic cells resembled mature lymphocytes. The advent of flow cytometric immunophenotypic analy sis has revolutionized our approach to this category of disease, because many distinctive B-and T-cell leukemias are now recognized (1,2). In most instances, rendering an accurate diagnosis is clinically important, because a specific therapy may be indicated. The ap proach to diagnosis often involves a multiparameter analysis, including careful morpho logical assessment, flow cytometrical immunophenotypical analysis, cytochemistry, cyto genetic, and molecular genetic studies. Major advances in diagnostic techniques, in particular the correlation of peripheral blood morphology with histopathology of biopsy sections and improved molecular/cytogenetic knowledge has made it necessary to revise both the approach and the classification of the CLLs. This chapter will first list the reactive disorders characterized by a peripheral blood lymphocytosis, followed by a discussion of the chronic B-cell lymphocytic leukemias. A detailed discussion of B-cell prolymphocytic leukemia (PLL) and the group of T-cell chronic leukemias will not be included, because these are discussed elsewhere.
