RET and cholangiocarcinoma: One study in pediatric thyroid cancers found that patients with RET or NTRK fusions were more likely to have metastatic disease and worse outcomes than those with BRAF-mutant disease.56 In contrast, another study found that non-RET fusions were more invasive than RET fusions in pediatric thyroid cancer but similarly invasive to BRAF-mutated tumors.57 In cholangiocarcinoma, FGFR2 fusions were grouped in a cluster of genetic alterations with the best prognosis.58 Thus, it seems the metastatic potential and prognosis is likely associated with specific fusion mutations rather than fusions per se.