2580 Nothing but NET: A Case of Neuroendocrine Tumor in the Duodenal Bulb

Abstract

INTRODUCTION: Neuroendocrine tumors (NETs) are rare neoplasms that comprise approximately 2% of all malignant tumors in the gastrointestinal system. The ileum remains the most common site of NETs in the small intestine, making up >70% of small bowel NETs. Duodenal NETs are exceedingly rare, comprising 2-3% of all gastrointestinal NETs and 1-3% of all duodenal tumors. We present a rare case of a patient diagnosed with a duodenal bulb NET. CASE DESCRIPTION/METHODS: A 66-year-old male with a past history of gastroesophageal reflux disease and hypertension presented to the gastroenterology clinic with a chief complaint of intermittent halitosis for the past year. The symptoms were unrelated to food intake. His recent dental examination was normal. He did not have a family history of gastrointestinal malignancies. His physical examination was unremarkable. Laboratory data including Helicobacter pylori antigen was unremarkable. He underwent esophagogastroduodenoscopy which demonstrated a 15 mm nodule in the duodenal bulb (Figure 1). Histopathological examination of the nodule showed a well-differentiated neuroendocrine tumor. Neuroendocrine immunohistochemical stains were positive for chromogranin and synaptophysin. Ki-67 was positive in 1% of tumor cells. CT scan of the abdomen revealed a 1.2 × 0.8 × 0.7 cm well-defined hyperattenuating structure in the posterior wall of the duodenal bulb (Figure 2). On endoscopic ultrasound, the lesion appeared to be located within the deep mucosa and submucosa without invasion of adjacent structures (Figure 3). The patient has been referred to medical oncology. DISCUSSION: The duodenum is an uncommon location for NETs. Duodenal NETs are typically small, single-lesion neoplasms, the majority of which are non-functional and diagnosed during the 6th decade of life. Unlike NETs of the jejunum and ileum that lack a gender preference, duodenal NETs carry a slight male predominance. Metastasis to regional lymph nodes is seen in ∼60% of cases and to the liver in less than 10% of cases. The absence of neuroendocrine clinical syndromes in >90% of duodenal NETs coupled with the rarity of this malignancy creates a noteworthy diagnostic challenge. It is therefore not surprising that the majority of these cases are diagnosed incidentally during work-up for other symptoms. With a rising annual incidence of NETs, it is important for gastroenterologists to keep this diagnosis in mind as a differential for any nodule in the duodenum.