Prolymphocytic transformation of chronic lymphocytic leukemia. A report of three cases and review of the literature.

Three cases of prolymphocytic transformation of chronic lymphocytic leukemia (PLL-trs CLL) are described, and a review of the literature yields 15 additional cases. PLL-trs CLL may be recognized when two populations of cells are present and the number of prolymphocytes are greater than 15% admixed with the small round lymphocytes of CLL. Surface immunoglobulin intensity appears to be greater on the prolymphocytes than on the small lymphocyte in the same case, suggesting a clonal differentiation. At the time of transformation, the spleen is generally larger than at the time of diagnosis of CLL, and lymphadenopathy is variable. Transformation is thought to be associated with increasing refractoriness to treatment and shorter survival, although most of the deaths occurred in clinical Stages III and IV, known to have a poor prognosis. Similar features between PLL-trs CLL and so-called de novo PLL also suggest an evolutionary process. However, additional morphologic and immunologic studies in transforming CLL cases are necessary to answer this question.