S3442 A Trip Through the Pylorus - A Rare Case of a Gastric Adenocarcinoma Invading the Duodenum and Literature Reivew

Abstract

INTRODUCTION: We present a rare case in a 61-year-old African American who shows one such case an interesting case of multiple gastric adenocarcinoma involving the gastric antrum and pylorus that extended into the duodenum. CASE DESCRIPTION/METHODS: A 61-year-old male without medical history presented with abdominal pain of one month acutely worsening over the 2 weeks. The pain was diffuse in nature, 9/10 in severity, with decreased appetite and 25lbs weight loss without exacerbating or relieving factors. Physical exam showed for RUQ and LUQ tenderness. Hepatomegaly was present with a firm mass palpated below the epigastrium. Labs were unremarkable. CT of abdomen and pelvis with contrast revealed hypoattenuating lesions in liver and spleen. An enlarged, heterogeneous pancreatic head with dilated duct and multiple enlarged lymph nodes, including a necrotic lymph node were found with the latter causing mass effect of structure. The stomach had a suspicious gastric mass with irregular wall thickening along the greater curvature and mesenteric stranding. There were multiple omental masses, peritoneal masses in RUQ and LUQ with significant retroperitoneal and pelvic lymphadenopathy. Subsequent upper endoscopy showed an abnormal nodular mucosal area in the junction of gastric body and antrum with a large gastric polyp in the adjacent area that was biopsied. Initially the top differential was lymphoma on accord that it does not respect the gastric-duodenal junction however, the pathology report of the abnormal gastric tissue revealed a poorly differentiated gastric adenocarcinoma that also involved duodenal mucosa with loss of nuclear expression of PMS-2 and MLH-1. Helicobacter Pylori testing was also noted be positive. Patient was started on FOLFOX therapy without benefit. Treatment was switched to Pembrolizumab therapy as tumor was MMR deficient with good response. DISCUSSION: The incidence of duodenal invasion in lower stomach cancer ranges from 13.5 to 33.2% mainly based on populations of Asian heritage, where the prevalence of gastric cancers is much higher than the rest of the world. Our patient is an African American male, and at the time of writing this case report our search showed that there are a handful of published cases of gastric cancer invading the duodenum in which highlights this rarity. We hypothesize that the reduced presentation of similar presentations may be low due to overall low incidence of gastric cancer in the United States, which has rapidly declined over the past 50 years.Figure 1.: Gastric antrum polyp.Figure 2.: Pre-pyloric tissue extending through pylorus into duodenal bulb.Figure 3.: Duodenal Bulb – Abnormal mucosa.