Relapse of acute lymphoblastic leukaemia 14 years after presentation: use of molecular techniques to confirm true re‐emergence

Late relapse after successful treatment of acute lymphoblastic leukaemia (ALL) in children is well-recognized but rare. It is often uncertain whether this represents a true relapse of the original disease or a second malignancy. We present the case of a patient who relapsed 14 years after the original diagnosis of childhood ALL in whom both the original leukaemic cells and those taken at relapse had an identical T cell receptor gamma (TCRG) gene rearrangement. This analysis confirms that this relapse is a true re-emergence of the patient's original disease. The term 'cure' should be used with caution in childhood ALL, even after long periods in continuous remission.