Clonal stability in late-relapsing childhood lymphoblastic leukaemia.

We report stability of a clonal immunoglobulin heavy chain (IgH) gene rearrangement in a case of childhood acute lymphoblastic leukaemia (ALL) relapsing 17 years after completion of first-line therapy. Clonal stability was shown by polymerase chain reaction amplification of the hypervariable CDRIII region of IgH gene. Identically sized products from the original diagnostic and the second presentation samples were obtained and direct sequencing confirmed complete sequence homology. Absence of clonal evolution together with recent reports of persistent minimal residual disease in patients in long-term complete remission, suggests that 'cure' of childhood ALL may be critically dependent on effective immune surveillance to keep such disease below clinically significant levels.