1861 Duodenal Gangliocytic Paraganglioma in Patient With Rectal Adenocarcinoma

Abstract

INTRODUCTION: Gangliocytic paragangliomas are a rare subclass of neuroendocrine tumors that usually appear in the periampullary region of duodenum. They are generally benign, although may have potential for metastases depending on size and extension. They most commonly present with bleeding or abdominal pain, but cases with obstructive jaundice and pancreatitis have also been reported. They are often misdiagnosed as GISTs or other neoplasms, but with histologic examination, an accurate diagnosis can be reached. However, intraoperative diagnosis with FNA and frozen section analysis are often inaccurate and could affect surgical decision. CASE DESCRIPTION/METHODS: 62-year-old male with past medical history of diverticulitis, internal hemorrhoids, and iron deficiency anemia presented with syncope and gastrointestinal bleeding. During evaluation with colonoscopy, a mass was found in the rectum, which was later confirmed to be an adenocarcinoma. An FDG-avid duodenal segment was incidentally found while undergoing workup with PET-scan. He had neoadjuvant chemoradiation, with resection of rectal cancer and temporal ileostomy. Biopsy of duodenum with endoscopic ultrasound revealed normal duodenal mucosa on 2 separate occasions. Ultimately, the duodenal tumor was excised via exploratory laparotomy. Intraoperative frozen biopsy of mass revealed a GIST and a Whipple procedure was performed due to proximity to ampulla. Final pathology report revealed a gangliocytic paraganglioma, after staining positive with synaptophysin (as well as S-100 and neuron specific enolase) and negative for antibody to CD117, which is a sensitive marker for GISTs. DISCUSSION: Duodenal gangliocytic paragangliomas remain to be rare entities. There is yet no clear consensus in regards to appropriate workup, treatment or follow-up, especially in patients with metastases or concurrent adenocarcinoma. It is uncertain if coexistence with a rectal adenocarcinoma (as seen in this case) was coincidental or due to similar pathogenesis. Diagnosis with FNA and frozen section biopsies can be useful, but are often inaccurate. The success largely relies on the operator and clinical suspicion, but it is especially hard when there are no symptoms or relevant history. The recommended management is margin-free resection endoscopically, with local surgical excision or Whipple procedure. Studies have shown that some molecular markers can predict malignant potential. Yet, whether they are useful for management or surveillance has not been determined.