A case of lung cancer metastasized to the gastrointestinal anastomosis site where the primary gastric cancer was resected 17 years ago.

Metastasis from lung cancer, often found in the adrenal glands, bone, liver, brain, and kidneys, have been thought to be rare in the digestive system. When a metastatic tumor is found in the intestine, it is most commonly metastatic melanoma or carcinoma of the cervix uteri, ovary, or breast. Yet, intestinal metastases have been described in 11% of lung cancers at autopsy. These metastases may induce gastrointestinal perforation, obstruction, or bleeding. Patients with bleeding from small intestinal metastases secondary to lung cancer almost uniformly have poor prognoses. The lung cancer metastasized to the gastrointestinal site or location where a first primary cancer was once resected is never reported in the literature. We report the case of a 76-year-old man with a history of gastric adenocarcinoma treated by subtotal gastrectomy seventeen years ago who presented with lung cancer metastatic to the bone. One month later, he developed persistent melena due to duodenal metastases. Upper gastrointestinal endoscopy showed an ulcerative duodenal mass with bleeding. The pathohistological and immunohistochemical examinations of tissue from the pathologic fracture and the endoscopic biopsy specimen revealed metastatic poorly differentiated adenocarcinoma consistent with lung origin. The diagnosis of metastatic lung cancer can be rendered based on pathologic examination and immunohistochemical analysis, even without access to the primary lung tumor. In this case, the anastomosis site where a gastrectomy for gastric cancer was once performed might be a good niche or microenvironment for cancer cells or tumor stem cells to metastasize to.