Despite a polytypic pattern of light chain expression, the neoplastic nature of biclonal CLL is suggested by a characteristic CLL phenotype and can be confirmed by cytogenetic and genomic analyses. The two clones with discordant light chain isotypes may share a "stem-line" cytogenetic abnormality, suggesting possible clonal evolution. Biclonal CLL is associated with NOTCH1 mutations, which may occur in a small subclone and gradually evolve in clonal size. Genomic analysis on light chain-sorted and/or chronologically collected samples may provide insight into clonal evolution in CLL.
Chronic Lymphocytic Leukaemia (CLL) is the most common adult B-cell leukaemia and despite improvement in patients' outcome, following the use of targeted therapies, it remains incurable...