Jh gene sequence analysis in a patient with Waldenström's macroglobulinaemia with subsequent development of immunoblastic lymphoma.

A case of Waldenström's macroglobulinaemia with subsequent development of immunoblastic lymphoma in a 69 year old man is reported. Plasmacytoid lymphocytes were initially observed in both peripheral blood and bone marrow smears. Lymph node biopsy was interpreted as malignant lymphoma, diffuse mixed cell type compatible with Waldenström's macroglobulinaemia. Complete remission resulted on combined treatment with prednisolone and melphalan. Four years later, lymphadenopathy recurred and biopsy revealed the development of an immunoblastic lymphoma. Initially, this lymphoma was thought to be the malignant transformation of Waldenström's microglobulinaemia, because both tumours produced IgM (kappa light chains). Sequencing of immunoglobulin heavy chain genes ofWaldenström's macroglobulinaemia and immunoblastic lymphoma cells, however, revealed different Dh and Jh usage between the two, indicating the independent nature of the two haematological malignancies. These results indicate that clonality of primary and secondary tumours should be determined not by phenotypic, but by genotypic analysis.