BRAF mutations are found in a wide range of both solid and haematopoietic tumours, with a particularly high incidence in benign melanocytic nevi, malignant melanoma, papillary carcinoma of the thyroid [16], and the primary histiocytic disorders, Langerhans cell histiocytosis (LCH) and Erdheim–Chester disease (ECD) [17,18]. This evidence concerns the gene BRAF and Langerhans cell histiocytosis.