A further example was case 1, in which it was not possible to distinguish between the recurrence of a Wilm’s tumour and a radiation-induced sarcoma using standard testing; the presence of ATRX/RAD51B deletions and the confirmation of the absence of any recurrent Wilm’s tumour associated variants anywhere in the genome allowed a confident diagnosis of an undifferentiated sarcoma. The gene discussed is RAD51B; the disease is undifferentiated (embryonal) sarcoma.