BRAF and gastrointestinal stromal tumor: It is estimated that the BRAF mutation occurs in almost all hairy cell leukemias, at least 50% of melanomas, 40% of thyroid cancers, 10% or less of colorectal cancers, and rarely in clear cell sarcomas (CCSs) and gastrointestinal stromal tumors (GISTs)4, 22, 24, 25 (Figure 5A).