Second, subsite differences may be due to differences in tumor methylation status, BRAF (gene encoding for b-raf i.e. rapidly accelerated fibrosarcoma) and KRAS (proto-oncogene that acts as an on/off switch in cell signaling, named after Kirsten RAt Sarcoma virus) mutation status, as well as DNA microsattelite instability. Here, KRAS is linked to fibrosarcoma.