Richter's syndrome with identical immunoglobulin gene rearrangements in the chronic lymphocytic leukemia and the supervening non-Hodgkin lymphoma.

In a patient who developed Richter's syndrome, complex cytogenetic abnormalities of the centroblastic non-Hodgkin lymphoma (NHL) was associated with chemotherapy resistance. The clonal origin of the preexisting chronic lymphocytic leukemia (CLL) and the subsequent NHL cells was investigated. Both cell populations were present in the peripheral blood and could be separated efficiently by counterflow centrifugal elutriation. In the lymph node biopsy mainly NHL centroblasts were found and only a minor population of small lymphocytes. The separated CLL and NHL cells from blood as well as the lymph node cells were found to express mu and kappa Ig chains. Since expression of identical light chains is not synonymous with common clonal origin, Southern blot analysis of the Ig heavy chain genes was also performed, which showed that the two cell populations had identical Ig heavy chain gene rearrangements. Therefore, it was concluded that the CLL cells and the NHL cells in the present case originate from the same precursor cell and that the NHL has to be regarded as a malignant progression of the CLL. These findings are different from our previous report on another patient with Richter's syndrome, in whom the CLL and the NHL represented two unrelated malignancies. Therefore, the occurrence of NHL in Richter's syndrome apparently may represent either a clonal progression of the CLL or a second lymphoid malignancy.