A 50-year-old woman presents with duodenal ulcer disease and high basal acid secretory outputs. Secretin stimulated serum gastrin levels are in excess of 1000pg/mL. She has a long history of ulcer disease that has not responded to intense medical therapy. What is the most likely diagnosis?

ZES is characterized by duodenal ulcer dis- ease, high basal acid secretory output, and a pancreatic tumor. Stimulated serum gastrin levels may be in excess of 1000pg/mL or as high as 10,000pg/mL. ZES is due to a true pancreatic tumor in adults but may be secondary to hyperplasia in children. Growth of the tumor is usually slow and survival is often prolonged. If an isolated tumor is found on CAT scan, surgical resection is indicated. About two-thirds of these tumors are malignant. About one-fourth of patients have MEN I syndrome tumors of parathyroid pituitary and pancreas.