Melanoma is the second most frequent tumor in which BRAF mutations are observed (60% of cases), preceded by hairy cell leukemia (100%), and followed by papillary thyroid cancer (40–60%); BRAF mutations have also been identified, albeit at a lower percentage, in astrocytomas (10–15%), colorectal cancer (5–10%), non-small-cell lung carcinoma (3–5%), and other clonal diseases, such as Langerhans and non-Langerhans cell histiocytosis [100,101]; based on this broad occurrence, BRAF mutations represent a critical therapeutic target in cancer therapy. This evidence concerns the gene BRAF and hairy cell leukemia.