Biclonal composite lymphoma. A multiparameter flow cytometric analysis.

A case of composite, biclonal lymphoma detected and characterized by multiparameter flow cytometric analysis is presented. Analysis of cell surface immunophenotype and cell size, as assessed by forward light scatter, revealed that two populations of cells were present. The small cells were monoclonal kappa-positive cells admixed with reactive T and B cells. The large cells reacted solely with anti-lambda antibodies. Dual-color and dual-parameter (surface vs DNA) analysis further showed that the small, kappa-positive cells coexpressed CD5 and were diploid, with an estimated synthetic (S) fraction of 2.2%. The predicted histologic pattern was malignant lymphoma, small lymphocytic. In contrast, the large lambda-positive cells were both hyperdiploid and tetraploid with an estimated S fraction of 18%. On the basis of this multiparametric analysis, the predicted histologic pattern for the latter component was malignant lymphoma, diffuse large-cell type. Subsequent histologic examination confirmed the predicted pattern in both cases.