"Composite" lymphoma, lymphoplasmacytoid and diffuse large B-cell lymphomaof the spleen: molecular-genetic evidence of a common clonal origin

We describe here the first well-characterized case of '"composite" lymphoma of the spleen in which the two components were a low-grade and a high-grad e B-cell non-Hodgkin's lymphomas. The patient was an elderly man with promi nent splenomegaly and multiple hypoechogenic lesions of the spleen. A splen ectomy was performed, and the macroscopic and histological findings showed the simultaneous presence of a "low-grade" B-cell lymphoma, lymphoplasmacyt oid (immunocytoma) and a "high-grade" B-cell lymphoma (immunoblastic), whic h were spatially separated. The two lesions expressed the same immunoglobul in light chain (lambda), but the Southern blot analysis showed differ-ent p atterns of immunoglobulin heavy chain (IgH) clonal rearrangement. PCR analy sis followed by direct sequencing of the IgH-amplified rearrangement produc ts provided molecular-genetic evidence that the two components of the compo site lymphoma had the same clonal origin. Since both EBV LMP-1 and p53 were negative by immunohistochemistry, it is unlikely that EBV and p53 were inv olved in the neoplastic progression in this case. PCR analysis and direct s equencing of IgH-amplified rearrangement products are useful tools to inves tigate clonality in eases in which Southern blot analysis cannot be perform ed or does not provide conclusive findings.