Overall, different samples had different dominant mutational signatures, but we also found that the AID/APOBEC-related signatures, including Signature 13 and Signature 2, were the top two contributing signatures across all samples, and the overall pattern of the mutation spectrum in metastatic tumour samples was similar to that of primary and regional lymph node tumour samples (Supplementary Fig. 1f; Supplementary Fig. 2a). This evidence concerns the gene AICDA and metastatic neoplasm.