What is the recommended management for a patient with a history of gastric NET and elevated gastrin levels who presents with a small sessile Paris IIa polyp during EGD surveillance?

Management of Small Gastric Polyp in Post-Gastrectomy Patient with Elevated Gastrin and History of Gastric NET

For this patient with persistent hypergastrinemia after gastric NET resection who presents with a small (<5 mm) sessile polyp, the priority is to determine the NET type through gastric pH measurement and continue structured endoscopic surveillance every 6-12 months, with histologic evaluation of the biopsied polyp to guide further management. 1

Immediate Diagnostic Steps

Confirm True Hypergastrinemia

• Stop proton pump inhibitors (if taking) for 10-14 days and remeasure fasting gastrin levels, as PPIs commonly cause spurious elevation and can confound interpretation 2, 3
• This step is critical before proceeding with further workup, as false elevations are common 4

Determine NET Type via Gastric pH

• Measure gastric pH to distinguish between Type 1 and Type 2 gastric NETs 1:
  • pH >4-5 indicates Type 1 NET (achlorhydria from atrophic gastritis) - accounts for 70-80% of gastric NETs with low metastatic potential 1
  • pH <2 indicates Type 2 NET (gastrinoma/Zollinger-Ellison syndrome) - requires aggressive workup for gastrinoma 1
• This single test is the key discriminator and determines the entire management pathway 1

Management Based on NET Type

If Type 1 Gastric NET (Most Likely Given History)

• Continue surveillance endoscopy every 6-12 months for the first 3 years, then annually thereafter 2, 1
• The small polyp (<5 mm) that was biopsied should be evaluated histologically; if it represents recurrent NET, this falls within expected surveillance findings 2
• Consider antrectomy only if new lesions develop or increasing tumor burden is observed - not indicated for stable small polyps 2, 1
• Gastrin levels will remain persistently elevated due to atrophic gastritis and are generally uninformative for monitoring 2

If Type 2 Gastric NET (Less Likely but Must Exclude)

• Obtain multiphasic CT or MRI of abdomen/pelvis to locate duodenal or pancreatic gastrinoma 1, 4
• Use endoscopic ultrasound (EUS) for small duodenal gastrinomas that may be missed on cross-sectional imaging 1
• The goal is to locate and resect the gastrinoma, which is the underlying driver 1
• Consider secretin stimulation test if diagnosis remains uncertain after imaging 2

Polyp-Specific Management

For the Biopsied Polyp

• Await histopathology results from the cold forceps biopsy already performed 2
• If histology confirms NET G1 and the polyp is <5 mm, complete endoscopic resection is not mandatory at this size, but close surveillance is essential 2
• If the polyp shows dysplasia or grows beyond 1 cm on subsequent surveillance, complete endoscopic resection is indicated 2

Background Mucosa Assessment

• Carefully evaluate the remainder of the stomach for synchronous neoplasia, extent of gastric atrophy, and intestinal metaplasia 2
• This is particularly important in the post-gastrectomy stomach, where hyperplastic polyps can harbor dysplasia (1.9-19%) and malignant transformation risk is elevated 2

Ongoing Surveillance Strategy

Surveillance Intervals

• Perform endoscopy every 6-12 months for up to 3 years, then annually for up to 10 years 2, 1
• Ongoing surveillance is mandatory given the elevated risk of metachronous neoplasia in gastric NET patients 1
• Some guidelines suggest indefinite surveillance for Type 1 gastric NETs 1

Biochemical Monitoring

• Chromogranin A levels can be followed (though less useful in Type 1 NETs with atrophic gastritis) 2, 4
• Rising chromogranin A in an asymptomatic patient with stable imaging does not necessarily mandate new therapy 2, 4
• 24-hour urinary 5-HIAA is generally not useful for gastric NETs unless there is evidence of metastatic disease with carcinoid syndrome 2

Critical Pitfalls to Avoid

• Do not interpret elevated gastrin as disease progression in Type 1 gastric NETs - it reflects the underlying atrophic gastritis, not tumor activity 2
• Do not measure gastrin while patient is on PPIs - this causes false elevation and misinterpretation 2, 3, 4
• Do not assume all small polyps are benign - even small polyps in the post-gastrectomy stomach warrant histologic evaluation given increased malignancy risk 2
• Do not discontinue surveillance after initial resection - metachronous lesions are common and require ongoing monitoring 1

Additional Considerations for Post-Gastrectomy Context

• The post-gastrectomy stomach has increased risk of dysplasia and malignant transformation in polyps compared to intact stomachs 2
• Multiple small polyps in the fundus and body in a patient with prior gastric NET and elevated gastrin strongly suggest Type 1 gastric NET with ECL cell hyperplasia 2
• Screen for MEN1 syndrome if Type 2 NET is confirmed by measuring fasting calcium, parathyroid hormone, and prolactin 2