2707 Gastric Mucosa-Associated Lymphoid Tissue Lymophoma Treated by Endoscopic Mucosal Resection

Abstract

INTRODUCTION: Primary low-grade gastric Mucosa-associated lymphoid tissue (MALT) lymphoma is a distinctive type of B-cell lymphoma. Endoscopic appearances of low-grade gastric MALT lymphoma are quite varied and polypoid or subepithelial type (exophytic) is rare. Here, we reported the case of H. pylori negative gastric MALToma presenting as an exophytic subepithelial tumor, diagnosing and treating by endoscopic mucosal resection (EMR). CASE DESCRIPTION/METHODS: A 53-year-old man was referred to our hospital because of a large subepithelial tumor of the stomach, which was incidentally found on an endoscopy for a routine checkup in outside hospital. Initial outside endoscopic biopsy was a simple chronic gastritis. Physical examination and laboratory results were unremarkable. On endoscopic examination, a 2.0 cm sized round and hard exophytic subepithelial tumor was seen on the great curvature side of high body of the stomach. The tumor showed a well-demarcated smooth border without any erosion and ulceration. An abdominal pelvic CT demonstrated an enhancing subepithelial tumor without regional lymphadenopathy, such as gastrointestinal stromal tumor. EUS showed a hypoechoic and heterogeneous mass in the 2nd and 3rd layer with ill-defined internal margin. EMR was done for both the definite diagnosis and the treatment without complications because the tumor had a semipedunculated morphology. Results of a histopathologic examination of the resected tumor showed diffuse lymphocytic proliferation in the submucosa mimicking a subepithelial tumor with lymphoepithelial lesions. Dense lymphocytic infiltration composed of mainly B cells forming vague follicular colonization. Immunohistochemical stain of cytokeratin also showed presence of lymphoepithelial lesions. The Ki-67 was positive in 7%. Histologically, no H. pylori was observed in the luminal side. Finally, the patient was diagnosed as a H. pylori–negative extranodal marginal zone B-cell lymphoma (MALToma) (stage EI1). No additional treatment such as chemotherapy or radiation was performed. The follow-up endoscopic examination showed no recurrence until 2 years after EMR. DISCUSSION: We suggest that EMR may be an alternative treatment modality in the diagnosis and the treatment of gastric MALT lymphoma in cases of submucosal or polypoid morphology type, especially when H. pylori is negative. Further study in terms of feasibility, efficacy, and long-term safety of EMR as a curative treatment would be warranted.