A distinctive composite lymphoma consisting of clonally related mantle cell lymphoma and follicle center cell lymphoma

Although follicle center cell lymphoma and mantle cell lymphoma are both B cell non-Hodgkin's lymphomas (NHL), they are regarded as separate entities with distinct clinical, morphological, immunophenotypic and molecular characteristics. To our knowledge, the coexistence of these 2 lymphomas in the same patient has never been reported. We describe a 70-year-old woman with a long-standing history of follicle center cell lymphoma, cytological grade I, who subsequently developed a composite lymphoma consisting of well-demarcated foci of persistent follicle center cell lymphoma surrounded by mantle cell lymphoma. This morphological interpretation was supported by the presence of both bcl-1 and bcl-2 gene rearrangements, which are molecular genetic hallmarks of mantle cell lymphoma and follicle center cell lymphoma, respectively. Polymerase chain reaction (PCR) analysis for rearranged immunoglobulin heavy chain (IgH) genes showed a dominant band identical in size in microdissected tumor cells of the follicle center cell and mantle cell lymphomas. Cloning and sequence analysis of the PCR products revealed a common clone-specific IgH gene rearrangement in these 2 lymphomas. These findings suggest that this composite lymphoma represents the unusual evolution of a malignant B-cell clone that resulted in the development of 2 morphologically distinct but clonally related B-cell NHLs. These findings also show the importance of integrating morphological, immunophenotypic, and molecular data to enhance our understanding of the complex pathogenic interrelationships in lymphomagenesis. (C) 1999 by W.B. Saunders Company.