Small Intestinal Metastasis From Pulmonary Large Cell Carcinoma Detected by Capsule Endoscopy and Balloon-assisted Endoscopy, Followed by Early Surgical Resection: A Case Report.

Metastasis of lung cancer to the small intestine is rare and often diagnosed only after life-threatening complications such as perforation or obstruction. We report a case of small intestinal metastasis from pulmonary large cell carcinoma, diagnosed using balloon-assisted endoscopy (BAE) performed for obscure gastrointestinal bleeding (OGIB). A 73-year-old male patient previously underwent right upper lung lobectomy for stage IA1 large cell carcinoma. At 4 months postoperatively, he presented with melena and anemia. Upper and lower endoscopy and computed tomography failed to identify the bleeding source, prompting capsule endoscopy (CE), which revealed a jejunal ulcer. Subsequent BAE revealed an ulcerative lesion with submucosal tumor-like elevated margins. Histopathological examination of the biopsy specimen showed proliferation of atypical cells with large nuclei, morphologically consistent with the previously diagnosed lung carcinoma. Considering the patient's good performance status and the presence of a solitary lesion, laparoscopic small bowel resection was performed. Histopathological findings of the resected small bowel specimen were consistent with the primary pulmonary lesion. The patient received postoperative chemotherapy and has remained recurrence-free for 1 year. This case underscores the significance of CE and BAE in evaluating OGIB, particularly in patients with a history of lung cancer. Early endoscopic diagnosis may facilitate timely surgical intervention and enhance patient outcomes.