Gastric cancer in Lynch syndrome observed by image-enhanced endoscopy.

A 66-year-old woman with a diagnosis of Lynch syndrome with MSH2 mutation was referred to surveillance EGD. Her medical history included multiple cancers: 3 gastric, a duodenal, 4 colorectal, an endometrial, and a bladder cancer. EGD showed a pale-colored, 2-tier raised lesion without a clear demarcation line in the upper part of the remnant stomach (A). Texture and color enhancement imaging enabled visualization of the clear boundary (B, arrows). Magnifying endoscopy with narrow-band imaging revealed a lobular surface structure that contained looplike microvessels, with a demarcation line (C). The results of serology and urea breath test for Helicobacter pylori were negative. These endoscopic findings suggested an early gastric cancer, which was extending laterally, measuring ≥10 mm. The lesion was subsequently resected en bloc by endoscopic submucosal dissection. On histologic examination, the tumor, 22 × 15 mm, showed monotonous proliferation of foveolar-like atypical tubules having enlarged nuclei and an irregular structure (D). The horizontal and vertical margins were free of tumor cells. Immunohistochemically, the tumor cells were positive for MUC5AC and MUC6 and negative for MUC2, CD10, pepsinogen I, and proton pump. Ki-67–positive cells were located at the whole mucosal layer. MLH1 and PMS2 were preserved, and MSH2 and MSH6 were lost. The final diagnosis was early gastric cancer of a gastric phenotype restricted to the mucosal layer, in Lynch syndrome, without lymphovascular invasion.