Prognostic value of mouse red cell rosette formation in chronic lymphocytic leukaemia

Mouse red cell (MRC) rosette formation was studied in 20 malignant haemopathies. Only cells from chronic lymphocytic leukaemia (CLL) and hairy cell leukaemia (HCL) formed MRC rosettes with a high frequency. However, cells from 2 cases of CLL could not be demonstrated to form MRC rosettes, although they were undoubtedly found to be of B origin. These 2 cases presented as typical CLL, but they were observed to transform into a sarcomatous type after 5-6 months of evolution, suggesting that the study of MRC rosette formation might be of prognostic value in CLL.