Gastric metastasis from small bowel adenocarcinoma in a Lynch syndrome patient.

Gastric cancer is a Lynch syndrome (LS)-associated tumor, with the cumulative lifetime risk in LS patients estimated to be 5.8-13%. Hence, surveillance for gastric cancer is important for LS patients, especially in those with a family history of gastric cancer or of Asian descent. We report a very rare case of a LS patient who showed gastric metastasis from jejunal adenocarcinoma curatively resected 8 years prior. A 79-year-old female was diagnosed with a synchronous gastric submucosal tumor (SMT) and right-sided colon cancer. She was referred to our hospital as she and her family had histories of LS-associated tumors. She underwent curative intent surgery for the tumors. Postoperative histopathological examination revealed the gastric SMT was an adenocarcinoma completely covered by non-neoplastic gastric mucosa. Immunohistochemical analyses showed the gastric SMT had the same expression pattern for CDX2, cytokeratins 7 and 20 as the jejunal adenocarcinoma. Thirty-four months after surgery the patient is alive without recurrence or any other LS-associated tumors. To the best of our knowledge, this is the first report of gastric metastasis from small bowel adenocarcinoma in a LS patient. Awareness of this case may be important for gastric cancer surveillance in LS patients.