Unusual Presentation of a MALT Lymphoma as a Gastric Submucosal Mass

Abstract

Introduction: MALT lymphomas are the most common type of primary gastric lymphomas. Gastric MALT lymphomas tend to display indolent behavior, and usually present as a localized invasion of the mucosa with potential involvement of deeper layers of the stomach wall. It is rare to see MALT lymphoma present as an isolated submucosal gastric mass without involvement of the mucosa. Case Report: A 61-year-old female with no significant past medical history presented 7 months after a work-up for complaints of melena and hematemesis at an outside hospital and was found to have an obstructing distal subepithelial gastric mass with ulcerations and gastritis on EGD. Biopsies showed mild acute and chronic inflammation negative for H. pylori. An EUS FNA was completed at the outside institution, but the FNA was nondiagnostic. She was then referred to our institution for EUS and further evaluation. CT chest/abdomen/pelvis revealed a 3.6 x 2.1-cm gastric antral submucosal mass at the posterior wall. Upper endoscopy revealed a large subepithelial mass in the prepyloric antrum without bleeding. A heterogeneous round well-defined mass was identified endosonographically in the prepyloric region of the stomach arising from the submucosa without associated lymphadenopathy. FNA was then completed with a 22-gauge needle, and the specimen was sent for cytology and flow cytometry. In order to obtain more tissue for diagnosis, a 1-cm incision into the mass was then made with the needle-knife using a free hand technique. Jumbo biopsies were then taken from the submucosal tissue from the incisional site. An Endoclip was placed over the incision with good result. Biopsies from the submucosal lesion showed morphology and immunophenotype consistent with a marginal zone lymphoma. FNA of the submucosal mass showed an atypical lymphoid infiltrate. FISH showed the presence of t(11;18). A monoclonal kappa light chain expressing population of cells was positive for CD20/CD19 and negative for CD5/CD10. She was then referred for definitive radiation therapy after H.pylori treatment. The patient tolerated radiation therapy well, and complaints of abdominal pain, nausea, and vomiting resolved. A follow-up EGD with EUS exhibited that the submucosal lesion had resolved. Discussion: While MALT lymphomas are the most common primary gastric lymphomas, their presentation as a localized gastric submucosal mass remains extremely rare. The diagnosis of MALT lymphoma by endoscopic mucosal biopsy alone became challenging in this case due to the unusual presentation as a submucosal mass. Therefore, EUS with FNA and incision of the mass for deeper biopsies provided the most accurate diagnosis and may become an important way to evaluate submucosal gastric lesions.