Immunophenotypic Diagnosis of Leukemic B-Cell Chronic Lymphoproliferative Disorders Other Than Chronic Lymphocytic Leukemia

Leukemic B-cell chronic lymphoproliferative disorders (B-CLPD) are a relatively heterogeneous group of diseases, all of which exhibit a clonal expansion of mature-appearing B-lymphoid cells in the peripheral blood (PB). Both primary leukemias and the leukemic phase of primary lymphomas are included in this category (1). Among the primary B-cell leukemias, chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL), and hairy cell leukemia (HCL) are usually considered; within the primary lymphomas, follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone splenic lymphoma (MZSL), lymphoplasmacytic lymphoma (LPL), and the large B-cell lymphomas (LCLs) exhibit PB movement more frequently (1). At present, analysis of the immunophenotypic features of the clonal B-cells and study of their cytomorphological and histopathological characteristics are the most valuable tools for the diagnosis of this group of diseases (1,2). More recently, the information provided by conventional cytogenetic, molecular, and fluorescence in situ hybridization (FISH) studies has further contributed to a detailed characterization of these entities, providing the tools for an integrated classification of B-cell CLPD (1,2). Immunophenotypic studies have now been applied for more than two decades to the study of B-cell CLPD. From the diagnostic point of view, immunophenotyping has long been used for the screening of B-cell clonality and for the phenotypic characterization and subclassification of Bcell CLPD (3–6). More recently, it has also been employed for additional clinical purposes including staging of the disease (7), prognostic evaluation (8), monitoring of residual leukemic cells (9), and prediction of response to specific therapies such as those that use anti-CD20 monoclonal antibodies (10–12). Initially, most of the studies dedicated to the analysis of antigen expression in CLPD used microscopy-based techniques (13). However, in the last decade, multiparameter flow cytometry has progressively replaced the microscope, and it is now the preferred method for the immunophenotypic identification, enumeration, and characterization of neoplastic B-cells in PB, 9