The patient was a boy aged 15 months at the time of enrollment with a phosphodiesterase 4D‐interacting protein (PDE4DIP)–NTRK1 fusion, localized, intramuscular soft‐tissue sarcoma…The patient subsequently was treated with 1 cycle of VAC with evidence of progressive disease despite treatment, followed by 1 cycle of chemotherapy with ifosfamide and doxorubicin. He continued to exhibit no response to systemic therapy...therefore treatment with larotrectinib was initiated...He achieved an initial partial response after 2 cycles of larotrectinib with a 37% reduction in tumor burden.