Independent clonal origin of T- and B-cell clones in a composite lymphoma.

We present a detailed immunohistological and genotypic analysis of an unusual case in which a peripheral T-cell lymphoma, with features of Lennert's and angioimmunoblastic lymphoma, occurred after treatment of a low grade plasmacytoid lymphoma. By analysis of immunoglobulin and T-cell receptor genes, we show that the two diseases had an independent clonal origin at the level of lymphoid commitment. However, by employing a novel polymerase chain reaction-based technique for analysis of B-cell clonality, we show the persistence of a residual minor clonal B-cell population in the subsequent T-cell lymphoma. Only 2 previous cases of composite lymphoma involving B- and T-cell clones have been demonstrated by molecular analysis. This study underlines the immunophenotypic and genotypic heterogeneity of peripheral T-cell lymphomas and illustrates an unusual disease course in which a T-cell lymphoma has arisen in the context of, and perhaps as a consequence of, a B-cell lymphoma.