Stefansson and his colleagues have made numerous pioneering discoveries of genome variants conferring risk of many common cancers. They have played a role in shaping the now commonly accepted new paradigm for understanding cancer: that it should be defined at least as much in molecular terms as in where it occurs in the body. deCODE published holistic evidence of this in a familial aggregation of all cancers diagnosed in anyone in Iceland over fifty years, as well as other aggregation studies. These have demonstrated through basic genetics that while certain site cancers clustered in families, others cluster in a non-site specific way, pointing to common molecular causes. They discovered the chromosome 8q24 locus as harboring risk variants for many types of cancer, and variants in the TERT, TP53 and LG24 genes as risk factors for multiple cancers.  