[Differential malignant lymphoproliferative syndrome (LPS) diagnosis with flow cytometry: a study of 100 patients]

The clinical utility of flow cytometry in diagnosis of chronic lymphoproliferative disorders (LPD) is well established. Accurate diagnosis of related but still distinct entities is relevant to therapeutic decisions. We report on the immunophenotypic findings of 100 patients with a new diagnosis of LPD established by two-color flow cytometry. A panel of > 15 monoclonal antibodies was regularly applied. The characteristic immunophenotype of B-cell chronic lymphocytic leukemia (CD5+, CD23+, FMC7-) was found in 74 patients including one with Richter's transformation. Hairy cell leukemia (CD5-, CD11c+, CD103+) was diagnosed in 6, and B-cell Non-Hodgkin lymphoma (B-NHL) in 13 patients, respectively. 6 of the B-NHLs belonged to the entity of splenic lymphoma with villous lymphocytes (CD5-, CD23-, FMC7+) and 6 were identified as mantle cell lymphomas (CD5+, CD23-, FMC7+). One B-NHL was typed as follicular center cell lymphoma (CD5-, CD10+, FMC7+). Three B-cell LPDs without a characteristic marker profile were histologically further classifiable. With a total of 4 patients T-cell LPDs were much less frequent. Sézary syndrome (CD4+, CD8-, CD56-) and T gamma lymphoproliferation (CD4-, CD8+, CD16-, CD56-, CD57+) were diagnosed twice. In 17 patients with a characteristic marker profile (1 Richter's transformation, 5 hairy cell leukemias, 3 splenic lymphomas with villous lymphocytes, 4 mantle cell lymphomas, 4 T-cell proliferations) a further histological or molecular investigation confirmed the immunophenotypic diagnosis in all cases. Clinical presentation with lymphadenopathies and B-symptoms was mainly associated with the diagnosis of mantle cell lymphoma, whereas splenomegaly and infection were suggestive of hairy cell leukemia. 94% of the B-CLL patients were diagnosed at an early clinical stage with still conserved hematopoiesis, 32% of the LPDs were diagnosed following a routine hematogramm.