Bowel obstruction caused by colonic metastasis of lung adenocarcinoma: a case report and literature review.

INTRODUCTION: Lung cancer is the most common cause of cancer-related deaths globally. Metastatic disease is often found at the time of initial diagnosis in the majority of lung cancer patients. However, colonic metastases are rare. This report describes an uncommon case of colonic metastasis from lung adenocarcinoma. CASE PRESENTATION: A 64-year-old female presented to her gastroenterologist for progressively worsening abdominal pain and constipation. Exploratory colonoscopy revealed a large rectosigmoid mass resulting in near total rectal occlusion. Her specialist recommended she immediately go to her regional hospital for further workup. On admission, she complained of continued abdominal pain and constipation. Notably, she had a past medical history of non-small cell lung cancer (T1bN3M0 stage IIIB), diagnosed 1 year prior. She was thought to be in remission following radiation and immunotherapy with pembrolizumab. Upon hospital admission, she underwent an urgent colostomy, ileocecectomy and anastomosis, and rectosigmoid mass resection with tissue sampling. Pathology confirmed the diagnosis of colonic metastasis from primary lung adenocarcinoma. Treatment was with systemic chemotherapy followed by localized radiation to the pelvic region was started. She did not respond well to these therapies. Subsequent imaging showed refractory tumor growth in the pelvic region. Treatment could not be completed due to the patient experiencing a debilitating stroke, and she was transitioned to hospice care. CONCLUSIONS: Clinicians should have a low threshold for intestinal investigation and considerations for colonic metastasis when patients with a history of primary lung cancer have abdominal symptoms.