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. The gene discussed is RET; the disease is metastatic neoplasm.