Mucinous adenocarcinoma of the stomach with difficult preoperative diagnosis

A 68-year-old man was referred to our hospital for anemia. Abdominal computed tomography showed wall thickening with calcification in the lesser curvature of the gastric pylorus. Upper endoscopy revealed a submucosal tumor-like lesion with multiple superficial irregular ulcers from the gastric angle to the lesser curvature of the antrum. However, biopsy from the ulcer margin detected group 2. After gastric antacid administration, the edematous changes at the ulcer margin improved, the tumor surface became apparent, and por1 was detected on biopsy. Distal gastrectomy with D2 lymph node dissection and Roux-en-Y reconstruction was performed, and the final diagnosis was muc >>por1, tub1, pStage IIB T3N1M0, gastric mucinous carcinoma. Submucosal tumor-like gastric cancer is mostly covered by non-cancerous mucosa, and the positive biopsy rate of gastric mucinous carcinoma is low (19-24%). Targeting the tumor surface at the edge of an ulcer by using antacids and image enhancement endoscopy during biopsy may increase the positive diagnosis rate.