Abstract: A retrospective analysis of a 63-year-old male patient with intussusception caused by small intestinal metastasis of lung cancer.The patient was admitted with aggravated abdominal pain and intestinal obstruction.Imaging examinations suggested small bowel intussusception and a lung mass.Emergency partial small bowel resection was performed.Postoperative pathology,combined with immunohistochemical findings,confirmed the diagnosis as small intestine metastasis from a SMARCA4-deficient undifferentiated carcinoma of pulmonary origin.The patient recovered well postoperatively and received tislelizumab immunotherapy.Follow-up for over 2 years showed the patient was still alive,although a later review indicated an increase in the size of the primary lung lesion.Small intestinal metastasis from lung cancer is clinically rare and challenging to diagnose.Surgical intervention can effectively manage acute complications,and combined with systemic therapy,may prolong patient survival.

Key words: lung neoplasms, small intestine metastasis, intussusception, immunohistochemistry