THE UTILITY OF FLOW CYTOMETRIC IMMUNOPHENOTYPIC ANALYSIS IN THE DISTINCTION OF SMALL LYMPHOCYTIC LYMPHOMA CHRONIC LYMPHOCYTIC-LEUKEMIA FROMMANTLE CELL LYMPHOMA

The clinical and morphologic distinction between small lymphocytic lym phoma (SLL)/chronic lymphocytic leukemia (CLL) and mantle cell lymphom a (MCL) is often challenging and has important prognostic and therapeu tic implications. The authors investigated the usefulness of the marke r CD23 in discriminating between these processes by flow cytometric im munophenotypic analysis. Consecutive samples of body fluids and hemato poietic tissue from patients with suspected B-cell lymphoproliferative disorders were studied using a panel of antibodies that included pan- B cell markers, CD5, FMC7, and CD23. Specimens from 38 patients with C DS-positive B-cell lymphoproliferative disorders consisting of a monom orphic population of small lymphoid cells were identified. Using stand ard flow cytometric and/or morphologic criteria, 28 patients were clas sified as having SLL/CLL and 10 were classified as having MCL. Neoplas tic cells from all 28 patients (100%) with SLL/CLL demonstrated CD23 i mmunoreactivity, whereas neoplastic cells from none of the 10 patients (0%) with MCL demonstrated CD23. immunoreactivity (P < .0001). FMC7 i mmunoreactivity was observed in one of eight cases of SLL/CLL and in f ive of five cases of MCL (P = .0047). In conclusion, CD23 is a useful marker for the subclassification of CD5-positive B-cell lymphoprolifer ative disorders by flow cytometric analysis. FMC7 also may be a useful marker for subclassification.