Early gastric cancer with lymphoid stroma presenting as a subepithelial lesion diagnosed by endoscopic submucosal dissection

A 53-year-old man underwent an esophagogastroduodenoscopythat showed a 20-mm subepithelial lesion in the middle gastric body. Endoscopic ultrasoundrevealed a hypoechoic mass located in the submucosa. Biopsy specimens revealed a benign gastric mucosa with severe lymphocytic infiltrationin the submucosa. Malignant lymphoma or gastric cancer with lymphoid stromawas suspected. We performed endoscopic submucosal dissectionfor definitive diagnosis. Histological examination showed undifferentiated adenocarcinoma, which showed positive Epstein–Barr virus-encoded RNA in situ hybridization results, invading the submucosamixed with dense lymphocytic infiltration. Thus, Epstein–Barr virus-positive gastric cancer with lymphoid stromawas diagnosed. Gastric cancer with lymphoid stromais a rare subtype of gastric cancer, which is associated with Epstein–Barr virus infection; it sometimes appears as a subepithelial lesion, which makes it difficult to diagnose using standard biopsy. Endoscopic submucosal dissectionwas useful in obtaining a sufficient tissue for full histological assessment, including immunostaining.