SUN-066 - Occult Gastrinoma with Isolated Nodal Metastases and Biochemical Cure after Resection

Zollinger–Ellison syndrome (ZES) results from gastrin-secreting neuroendocrine tumors (Gastrinomas). Diagnosis is often confounded by proton pump inhibitor (PPI) therapy, which can elevate gastrin levels and partially mask symptoms. Gastrinomas are frequently very small (often < 2 cm) and may metastasize early to regional lymph nodes or liver. When lesions are detected in these locations, distinguishing primary tumors from metastases can be challenging.
A 65-year-old woman with a history of Helicobacter pylori eradication presented with years of progressive abdominal pain, nausea, vomiting, diarrhea, weight loss, and recurrent hospitalizations. She underwent gastrojejunostomy tube placement without symptom relief. Repeated upper endoscopies demonstrated esophagitis, gastritis, and duodenitis despite high-dose PPI therapy. Fasting serum gastrin was 375 pg/mL while taking pantoprazole 40 mg twice daily and remained elevated at 299 pg/mL after a 4-week PPI washout (reference < 100 pg/mL). A 68Ga-DOTATATE PET/CT demonstrated two small foci of uptake in the distal duodenum/proximal jejunum near the ligament of Treitz. Chromogranin A was 1898 pg/mL; prolactin, VIP, and glucagon were normal. Parathyroid hormone was elevated at 173 pg/mL with normal serum calcium; MEN1 germline testing is pending.
The patient underwent exploratory laparotomy with intraoperative inspection and resection of nodules at the ligament of Treitz, fourth-portion duodenum and proximal jejunum. Pathology revealed metastatic well-differentiated neuroendocrine tumor in 2/10 lymph nodes (6.0 mm and 8.5 mm), positive for synaptophysin and gastrin, with Ki-67 ~1% (WHO grade 1). No primary tumor was identified in the resected bowel and no evidence of primary on imaging studies. Four weeks postoperatively, symptoms improved and fasting gastrin normalized to 15 pg/mL.
This case demonstrates an occult gastrin-secreting well-differentiated neuroendocrine tumor presenting with isolated nodal metastases and biochemical cure after nodal resection. It underscores the need to consider ZES in refractory ulcer/diarrheal syndromes despite PPI therapy and highlights the utility of 68Ga-DOTATATE PET/CT for localizing small-volume nodal disease when the primary tumor is not identified. Focused surgical resection can be both diagnostic and therapeutic in selected patients.

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