The relationship between chronic lymphocytic leukaemia and prolymphocytic leukaemia. II. Patterns of evolution of 'prolymphocytoid' transformation.

A series of 55 patients with B-cell chronic lymphocytic leukaemia (CLL) and prolymphocytic leukaemia (PLL) was studied in order to investigate the evolution of prolymphocytoid transformation of CLL. Peripheral blood films were assessed for the percentages of prolymphocytes (%PROL) during a followup period of 2 months to 24 years. The majority of patients with typical CLL (less than or equal to 10% PROL) had minor variations or transient increases in %PROL throughout the course of the disease, but in one third of them a steady rise in the proportion of these cells was documented. Patients presenting with 11-55% PROL, referred to as CLL/PL, exhibited three patterns of evolution: half of them showed stability of the PROL counts, one third had unsustained increases in the %PROL and 18% showed definite progression to a PLL-like blood picture. Patients diagnosed as PLL (greater than 55% PROL) had maintained a high %PROL during the period of observation. Serial marker studies in some CLL and CLL/PL cases showed that the percentage of M-rosettes and the intensity of SmIg remained at the same initial levels in all but two cases. These two cases in the CLL/PL group showed a significant decrease in the percentage of M-rosettes and stronger SmIg staining associated with progressive prolymphocytoid transformation. Patients with CLL and CLL/PL who had a sustained rise in the %PROL responded poorly to treatment compared with those with stable disease.