The B-RAF gene, which is also a member of the EGFR signalling pathway, is mutant in about 7-8% of tumours: mutations of this gene can be detected in ~45% of melanomas, ~40% of thyroid cancers, and 15% of colon cancers. Up to now, more than 100 different mutations of this gene have been described, but the most frequent is found in position 600 (V600E), which represents more than 90% of all mutations. Due to the BRAF V600E mutation, cells begin to grow in an uncontrolled way that is independent of the growth factor; thus, in the presence of this mutation EGFR inhibitor medicines are ineffective.