Prolymphocytoid transformation of CLL: a clinical and immunological study of 22 cases.

The clinical, morphological and immunological features of 22 cases of chronic lymphocytic leukaemia in 'prolymphocytoid' transformation (CLL-Pro) are reported. Immunophenotypic patterns in CLL-Pro differ from CLL by the appearance of significant (greater than 15%) FMC7-positive components and/or increased SIg densities in most cases. Membrane TU1 and MRBC receptor expression was similar to that found in typical CLL. Morphologically, all cases showed a mixture of small lymphocytes and larger nucleolated 'prolymphocytes' although the degree of prolymphocytoid change was unrelated to immunological patterns. Clinically, the cases behaved in a very heterogeneous fashion, with some patients dying rapidly following transformation despite treatment, while others even if untreated had a long, stable and relatively benign course. It was not possible to predict which patients would do badly from immunological or morphological features but the presence of more than one involved lymph node site and the occurrence of B-symptoms appeared to identify a group that did badly. Immunological assessments were however important in therapeutic terms, drawing distinction between CLL-Pro variants and prolymphocytic leukaemia (PLL).