KIT and neoplasm: A classic example of this is mutational profiling of KIT, PDGFRA, and other genes to predict sensitivity of gastrointestinal stromal tumors (GISTs) to imatinib and other KIT/PDGFRA tyrosine kinase inhibitors.6–11 More recently, the discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions as pan-tumor oncogenic drivers has provided new precision medicine-based treatment options for a subset of patients with sarcoma.12 The rarity and diagnostic complexity of this particular biomarker raise a number of questions and challenges for clinicians.