Prolymphocytic transformation of chronic lymphocytic leukemia.

This report describes eight patients with B-cell chronic lymphocytic leukemia whose disease became more aggressive over a variable period of time. This clinical progression was associated with a change in cell morphology from small lymphocytes to an increasing number of large transformed lymphocytes in the blood, bone marrow, and lymph nodes. In the peripheral blood, the predominant large cell was a prolymphocyte. The small lymphocytes and the prolymphocytes had identical cell surface markers in each patient. However, the prolymphocytes had a greater density of surface immunoglobulin than did the same lymphocytes. No features were found that help predict in which patients CLL will convert to a more aggressive form. Once transformation has taken place, however, there appears to be a correlation between the number of prolymphocytes in the blood and patient survival. It is suggested that the entities of prolymphocytic transformation of CLL, prolymphocytic leukemia, and Richter's syndrome are less distinct than has been thought previously. These disorders probably represent several phases of transformation of the same cell type, and they may be examples of different stages in the natural history of CLL.