Abstract
BACKGROUND: MET fusion is a key driver mutation, but it is rare in gastric cancer (GC). Several MET (hepatocyte growth factor receptor) inhibitors have been approved for the treatment of MET-positive patients, but the tumor response is heterogeneous. With the development of next-generation sequencing, diverse MET fusion partner genes have been identified. We herein report a fusion variant involving KIF5B-MET in GC. CASE SUMMARY: After thoracoscopic inferior lobectomy plus lymph node dissection under general anesthesia, a "tumor within a tumor" was found in the lung tumor tissue of a 64-year-old non-smoking male patient. Combining the medical history and the results of enzyme labeling, the focal area was considered to be GC. To seek potential therapeutic regimens, an intergenic region between KIF5B and MET fusion was identified. This fusion contains a MET kinase domain and coil-coiled domains encoded by KIF5B exons 1-25, which might drive the oncogenesis. CONCLUSION: Our finding could extend the spectrum and genomic landscape of MET fusions in GC and favor the development of personalized therapy.