Morphology and immunophenotype of chronic lymphocytic leukemia

Abstract

Chronic lymphocytic leukemia (CLL) is an indolent mature B-cell lymphoproliferative disorder that often presents with bone marrow and peripheral blood involvement. Lymphadenopathy and proliferation in extramedullary tissues are often seen. The key to the precise diagnosis of CLL begins with assessment of the cytomorphology of the neoplastic cells, often from peripheral blood, but also the architectural patterns of involvement from tissue sections in bone marrow and lymph node biopsies. Although not 100% sensitive and specific, these morphologic features are strong clues in the broad differential diagnosis. Immunophenotyping complements and aids the morphologic impressions. Although often an indolent disease, some patients tend to have progressive disease and an aggressive clinical course. Staining for CD38 and 70 kD zeta-associated protein (ZAP-70) helps to prognosticate the patient’s disease and predict the tumor’s mutational status for the immunoglobulin heavy-chain, variable region (IGHV). Since defining the disease in the mid-nineteenth century, the workup of CLL now combines multiple disciplines, from basic characterization of morphology to immunophenotyping, and now molecular genetics that all aid in arriving at a precise diagnosis and help to choose the proper therapies for affected patients. In this section, the morphology and immunophenotype of CLL are discussed, with special emphasis on differential diagnosis and transformation (Richter syndrome). The issue of monoclonal B-cell lymphocytosis is also addressed, the criteria and description of which have recently been modified in the new 2016 WHO revision.