These gene mutations were extremely rare in another primary CRC cluster, ‘C2’, which mainly harboured mutations in other SNV clusters, including nonsynonymous mutations in cell junction-related genes, such as DDX58, SDK1, and SORBS2, with significant functional impact scores based on SIFT (<0.05) [28] and POLYPHEN (p>0.85) [29] (Additional file 1: Table S5). Here, SDK1 is linked to colorectal carcinoma.