31st May 2023

A 61-year-old male presents to his GP with a 2-month history of weight loss and abdominal pain

A 61-year-old male presents to his GP with a 2-month history of weight loss and abdominal pain. He has been taking over the counter antacids for over a year for indigestion. His GP arranges for urgent endoscopy which demonstrates a shallow ulcer within the stomach and a positive CLO test. Histological analysis of biopsies taken from the ulcer reveals normal gastric epithelium, which is infiltrated by a neoplastic lymphocyte population, distributed within the marginal zone.

What is the most likely diagnosis?