A dramatic course after the resection of an SMARCA4-deficient undifferentiated tumour

Thoracic SMARCA4-deficient undifferentiated tumours are ordinarily found as a huge mass with systemic metastasis, and the prognosis is poor. The potential of immunotherapy for these unresectable tumours has been reported. An asymptomatic 68-year-old man with a smoking history had a left lung mass without distant metastasis and underwent complete resection. Two months after surgery, with no adjuvant therapy, he developed multiple distant metastases with aphasia and died 4 months after surgery. Adjuvant treatment may be necessary with immune checkpoint inhibitors, with a closer follow-up to detect recurrence without symptoms.