Small Bowel Perforation Caused by Metastatic Pulmonary Pleomorphic Carcinoma: A Case Report

Small bowel metastases from lung cancer are uncommon and may remain clinically silent until they present with bleeding, obstruction, or perforation. A 59-year-old man with a known history of lung cancer presented to the emergency department with diffuse abdominal pain that had worsened over the preceding three days, accompanied by nausea and vomiting. Records detailing the histological subtype, stage, and previous treatment of lung cancer were unavailable. On admission, the patient was hypotensive, tachycardic, and febrile, with generalized abdominal guarding. Contrast-enhanced abdominal computed tomography revealed pneumoperitoneum, jejunal wall thickening, inflammatory changes in the mesentery, and multiple necrotic lymph nodes. Emergency exploratory laparotomy revealed purulent intra-abdominal fluid, multiple stenosing small bowel masses, and perforation 50 cm distal to the ligament of Treitz. The affected bowel segment was resected, and intestinal continuity was restored through anastomosis. Histopathological examination revealed multiple tumor deposits involving the full thickness of the bowel wall, with an intact small bowel mucosa, lymphatic invasion, and metastases in both excised lymph nodes. The tumor cells were positive for thyroid transcription factor 1 and cytokeratin 7 and negative for cytokeratin 20. Together with the morphological findings, this immunoprofile supports small bowel metastasis from pulmonary pleomorphic carcinoma with non-small cell carcinoma features. Periodic acid–Schiff staining with diastase positivity indicated a focal, poorly differentiated adenocarcinoma component. Postoperative positron emission tomography/computed tomography revealed hypermetabolic lesions in the right lung, mediastinum, and abdomen. The patient recovered after surgery, was discharged on postoperative day 14, and subsequently received paclitaxel plus carboplatin therapy. Small bowel perforation should be considered in patients with lung cancer who present with acute abdominal symptoms, as prompt surgical intervention is essential to control this life-threatening complication.