B-Cell Chronic Lymphoid Leukemias

B-cell chronic lymphoproliferative disorders involving the blood or bone marrow encompass a wide spectrum of conditions, ranging from clinically indolent disorders to highly aggressive lymphomas/leukemias. At the indolent end of the spectrum is monoclonal B-cell lymphocytosis, which can be a normal finding in older individuals or show a low rate of progression to chronic lymphocytic leukemia. At the other end, aggressive lymphomas such as high-grade B-cell lymphoma may involve the blood in late-stage disease, which portends a very poor prognosis. Accurate diagnosis requires careful morphologic evaluation of the lymphoid cells in the blood or bone marrow in conjunction with clinical data and results of ancillary laboratory studies, particularly flow cytometry but also molecular and genetic studies.