Abstract
INTRODUCTION: Solid organ malignancies rarely metastasize to the duodenal papilla. We describe a case of primary lung cancer with duodenal papillary metastasis in a patient who presented with melena. To the best of our knowledge, this is only the second report of duodenal papillary metastasis from lung cancer. CASE PRESENTATION: A 65-year-old woman presented with complaints of anorexia, weight loss, and black stool. Imaging studies led to a clinical diagnosis of stage IVB lung cancer, and anticoagulants were initiated to treat pulmonary artery thrombosis. However, endoscopic hemostasis was challenging because of bleeding from a duodenal papillary tumor. Fortunately, the patient was positive for the plasma epidermal growth factor receptor (EGFR) gene mutation, and osimertinib, an EGFR tyrosine kinase inhibitor, was administered, successfully achieving hemostasis. Subsequently, endoscopic ultrasonography-guided transbronchial needle aspiration of an enlarged mediastinal lymph node and duodenal papillary tumor biopsy confirmed duodenal papillary metastasis of the primary lung adenocarcinoma. CONCLUSION: Although duodenal papillary metastasis is extremely rare, a good clinical outcome was achieved in this case by considering duodenal papillary metastasis from lung cancer as the differential diagnosis and administering systemic osimertinib therapy.