A novel TMTC2-NTRK3 fusion in undifferentiated high-grade pleomorphic sarcoma.

Undifferentiated high-grade pleomorphic sarcoma (UHPS) is a rare soft tissue sarcoma (STS) originated from mesenchyme. UHPS is mostly advanced, aggressive and has poor prognosis. Patients with UHPS tend to have a lower 5-year survival rate than patients with other types of STS. NTRK fusions are commonly found in rare histological tumor types. Among sarcomas, 90% of infantile fibrosarcomas have NTRK fusions. Many other types of sarcomas have also been studied for NTRK fusions. Targeted therapy with NTRK inhibitors, such as Larotrectinib and Entrectinib, leads to response in most patients with NTRK1/2/3 gene fusion-positive tumors. Herein, we present a 68-years old man with UHPS by pathological diagnosis. Next-generation sequencing (NGS) revealed a novel TMTC2-NTRK3 fusion, which was also detected by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). This report broadens the spectrum of NTRK fusions in UHPS and highlights a new target for treatment.