[Biclonal or biphenotypic chronic lymphotic leukemia? An answer brought by the treatment]

A 51-years-old patient with polyadenopathies presents a non monotypic chronic lymphocytic leukemia (CLL): lymphocytes B CD5+, CD23+, CD22-,CD79b dim, FMC7- express κ (71%) and λ (21%) light chains without coexpression. The caryotype shows two clones with one in evolution. Lymphoid clonality analysis by PCR (polymerase chain reaction) of the heavy and light chains genes of immunoglobulins shows two monoclonal rearrangements for each kind of chains. Lack of lymphoid cells sorting in function of the light chain doesn't allow us to conclude between a biclonal CLL and a biallelic monoclonal CLL. New adenopathies appearance in this patient, one year and a half after the end of his chemotherapy, leads to realisation of a new immunophenotyping: CLL is now monotypic with κ light chains expressed at 95%. In the new caryotype, only one clone is still present: it is the clone in evolution in the first caryotype and which presents additional abnormalities. This evolution allows us to assert the biclonality of the primitive CLL, the two clones evolving differently under treatment. In conclusion, the patient presented a biclonal CLL with one clone responding to treatment and the other one resistant.