Endoscopic submucosal dissection for protruding Helicobacter pylori-negative mucosa-associated lymphoid tissue lymphoma of the stomach: a case report.

Gastric mucosa-associated lymphoid tissue (MALT) lymphomas have various endoscopic appearances. We report a case of Helicobacter pylori-negative gastric MALT lymphoma with a protruding morphology similar to that of submucosal tumors. A 51-year-old man with a protruding tumor in the gastric cardia was referred to our hospital. Biopsy specimens showed no malignant epithelial tumors or lymphoid hyperplasia. Endoscopic submucosal dissection was performed and the patient was diagnosed with gastric MALT lymphoma. Lymphoma cells were present in the lamina propria mucosae and the submucosa under the non-atrophic fundic gland mucosa, with a feature of homogenous and monotonous growths, which was speculated to have resulted in a protruding morphology similar to that of submucosal tumors. Endoscopic submucosal dissection can be an alternative diagnostic option for gastric MALT lymphoma when the initial pathological diagnosis based on biopsy specimens is difficult.