CLL and diffuse histiocytic lymphoma in one patient: clonal proliferation of two different B cells

A case report is presented of a 77-year-old woman suffering from a composite lymphoma, known as Richter's Syndrome, consisting of chronic lymphocytic leukaemia (CLL) and diffuse histiocytic lymphoma. Light-microscopic investigation revealed the presence of CLL cells in the blood and bone marrow and a combination of CLL cells and large immunoblastic cells in the lymph node. Immunological investigation showed that both malignant cell types were B cells. The CLL cells carried a monoclonal surface immunoglobulin (S-Ig) micron lambda, and the immunoblastic cells had a monoclonal S-Ig micron K. These findings indicated that both clonal lymphoproliferative diseases were probably derived from different tumour stem cells.