CHRONIC LYMPHOCYTIC-LEUKEMIA WITH AN INTERFOLLICULAR ARCHITECTURE - AVOIDING DIAGNOSTIC CONFUSION WITH MONOCYTOID B-CELL LYMPHOMA

Certain low grade B-cell lymphoproliferative disorders can be mistaken for each other morphologically, particularly when there is partial ly mph node involvement. We encountered two cases of chronic lymphocytic leukemia, in which the interfollicular growth pattern and the pale app earance of the neoplastic proliferation in the lymph nodes led to a mi sclassification as monocytoid B-cell lymphoma. The correct diagnosis w as established, however, when the lymph node morphology was carefully reexamined, with the knowledge of the clinical history, peripheral blo od findings, and bone marrow data. The immunophenotype of the neoplast ic cells in the peripheral blood (CD5, CD23, weak fluorescence intensi ty of surface immunoglobulin and CD22) and the lymph node immunohistoc hemistry (weak L26 staining, strong MT1 positivity) confirmed the diag nosis of chronic lymphocytic leukemia. These two cases demonstrate the necessity of a systematic approach to lymph node morphology and the u tility of a multiparameter approach in the diagnosis of lymphoprolifer ative disorders.