Accelerated chronic lymphocytic leukaemia shows distinctive lymphocyte morphology in peripheral blood smears

Accelerated chronic lymphocytic leukaemia (A-CLL) is an aggressive variant of chronic lymphocytic leukaemia (CLL) characterised by distinct histologic features and a higher risk pathogenetic profile compared with conventional CLL (C-CLL). Although well recognised histologically, peripheral blood (PB) morphology of A-CLL is not well studied. In this study, we compared the PB lymphocyte morphology between 22 cases of biopsy-confirmed A-CLL and 60 cases of biopsy-confirmed C-CLL. PBs in A-CLL had a significantly lower percentage of typical CLL cells (mean: 51.28% vs 86.73%; p<0.001) and a higher percentage of classical prolymphocytes (12.11% vs 3.69%; p=0.021), non-classical prolymphocytes (17.48% vs 5.59%; p<0.001) and other atypical forms (cleaved, Downey-like and flower-shaped cells). Our data ties this distinct PB lymphocyte morphology in A-CLL with aggressive histology and a high-risk pathogenetic profile. Recognising the morphologic spectrum of PB lymphocytosis in A-CLL can facilitate earlier identification of this aggressive variant and help avoid misdiagnosis as other types of lymphoma/leukaemias.