B‐cell chronic lymphocytic leukaemia stage 0. An immunophenotypic study of 66 cases and comparison with B small cell lymphomas

Abstract:  The cells of 66 B‐CLL stage 0 patients were analyzed using a large panel of monoclonal antibodies in order to better define the immunophenotype of B‐CLL. The data were compared with the immunophenotypes of lymph node cells from 51 patients with diffuse B small cell lymphoma or leukaemia with lymph node enlargement. The most frequent immunophenotype of B‐CLL stage 0 was SIgM(D)⁺ EmR⁺ CD5⁺ CD9⁺ CD21⁺ CD23⁺ CD35^– CD38^–. Among the lymphomas, EmR‐positive and EmR‐negative cases were identified. The vast majority of the EmR‐positive cases usually showed the leukaemic pattern, immunophenotype and lymph node histology of B‐CLL. The EmR‐negative cases usually had immunophenotypes quite different from those of B‐CLL and the histology of indented cell lymphoma (centrocytic or intermediate) or features of lymphoplasmacytoid/cytic lymphoma. More than 20% of EmR‐positive cells proved to be the most important marker to distinguish B‐CLL from other lymphocytic lymphomas. Indeed this was a sign of better prognosis. Lymphoplasmacytoid/cytic lymphomas were EmR‐positive with the immunophenotype of B‐CLL or EmR‐negative with a definitely different immunological profile. This suggests two morphologically similar but biologically different subgroups of these diseases.