POLD1 and synovial sarcoma: Specifically, a recent study based on whole exome and SNP array based copy number analyses of CD4+ tumour cells of a large number of untreated SS patients showed various aberrations in genes related to DNA repair and genome stability, such as the POT1 and ATM genes responsible for telomere maintenance and genes associated to homologous recombination (RAD51C, BRCA2, POLD1) [40].