That principal melanocyte-specific signalling pathways controlling proliferation and differentiation operate through activation of B-raf possibly explains the high frequency of B-raf mutations in melanomas when compared to colon (18% of 40 cell lines and 12% of 33 tumours) or ovarian cancers (4% of 26 cell lines and 14% of 35 tumours, according to [3]), an exception being papillary thyroid carcinomas with 69% (24/35 cases positive, [41]) and 36% (28/78 cases positive, [42]) of the investigated cases, respectively. This evidence concerns the gene BRAF and differentiated thyroid carcinoma.