The most appropriate management is observation. This patient has a gastric neuroendocrine tumor (NET) that has developed in the presence of chronic autoimmune gastritis, which is characterized by pernicious anemia and hypergastrinemia due to achlorhydria or hypochlorhydria. Endoscopic polypectomy is considered curative treatment for this patient's NET. Gastric NETs are classified into three subtypes: type I, II, and III. This classification distinguishes the underlying pathogenesis and guides the appropriate management of the NET. Type I NETs account for the majority of gastric NETs, have an increased prevalence in older women, and are associated with autoimmune atrophic gastritis and hypergastrinemia. Type I gastric NETs are not associated with multiple endocrine neoplasia or Zollinger-Ellison syndrome (unlike type II gastric NETs) and rarely metastasize. Curative treatment of type I NETs is achieved with endoscopic removal of these lesions when they are small (<1 cm) and few lesions are present (<5), as is the case in this patient.

Tumor staging for type I gastric NETs (using CT of the abdomen and pelvis or radiolabeled somatostatin receptor scintigraphy) is not indicated because type I NETs rarely metastasize.

Surgical intervention is not indicated for this patient's small, type I NET that has been completely eradicated. Partial gastrectomy would be indicated if this patient's tumor was larger than 2 cm because of a risk of metastasis.