Richter's transformation in chronic lymphocytic leukemia.

Richter's syndrome (RS) is the development of high-grade non-Hodgkin's lymphoma (NHL) in patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma. This process may be triggered by viral infections (eg, Epstein-Barr virus infection), which are common in immunosuppressed patients. The large cells of RS either arise through a transformation of the original CLL clone or, less frequently, represent a new or secondary neoplasm. Karyotypic changes, including trisomy 12, chromosome 11 abnormalities, and multiple cell-cycle regulator disruptions, have been found in patients with RS. Although these genetic defects are believed to cause CLL cells to proliferate and, by facilitating the acquisition of new genetic abnormalities, to transform into RS cells, none appears predominantly responsible for the transformation. The prognosis is generally poor, and most patients do not have long-term (durable) responses to therapy. Rituximab and cytotoxic combination therapy followed by stem cell transplantation is associated with improved clinical outcome. Curative treatment strategies are needed.