S2964 A Double Whammy: Mixed Adenoneuroendocrine Carcinoma of the Stomach

Abstract

INTRODUCTION: Gastric Cancer is the fifth most common malignancy globally and the second in overall cancer-related mortality. A mixed adenoneuroendocrine carcinoma (MANEC) of the stomach is a rare condition defined by WHO as a tumor with both neuroendocrine as well as non-neuroendocrine or exocrine components. We present a unique case of a gastric MANEC. CASE DESCRIPTION/METHODS: An 84-year-old woman with a past medical history of hyperlipidemia, hypothyroidism, osteoporosis, gout was found to have a drop in Hb from 10.7 to 7.8 with melena. She underwent Esophagoduodenoscopy (EGD) which revealed multiple small and large gastric polyps throughout the stomach. Biopsies revealed well-differentiated MANEC. An endoscopic ultrasound (EUS) revealed the largest polyps measured 2.5 - 3.5 cm in size with some extending into the submucosa. Endoscopic mucosal resection was performed of the three largest polyps. Pathology revealed invasive moderately differentiated adenocarcinoma, limited to the muscularis mucosae with foci of well differentiated neuroendocrine tumor infiltrating the submucosa. The neuroendocrine tumor was strongly positive for synaptophysin and chromogranin with Ki 67 stain less than 2%. Subsequently, PET-CT scan was performed demonstrating minimal uptake localized to the borderline in size portocaval node with no enlarge or avid perigastric adenopathy. Case was reviewed at tumor board and is scheduled for a total gastrectomy. DISCUSSION: The diagnosis and treatment of gastric cancer has been an ongoing challenge facing modern gastroenterologists. MANEC is a rare condition which comprises both exocrine and endocrine tumors of at least 30% of each tumor component. These tumors often present with nonspecific clinical symptoms similar to those of conventional gastric cancer, many with metastatic disease. These cancers can be aggressive and are associated with poor prognosis. For tumors with neuroendocrine components, long acting somatostatin analogs can be used to halt proliferation of endocrine cells. They can also lead to regression of gastric neuroendocrine tumor and have proven to be a viable therapeutic option. Endoscopic submucosal dissection (or ESD) may be a feasible diagnostic and therapeutic option for gastric neuroendocrine or adenocarcinoma neoplasms. Additional treatment choice for MANEC is partial, subtotal, or complete gastrectomy depending on the location.Figure 1.: Endoscopic Image of Gastric MANEC.