Incidental diffuse gastric cancer in a patient with diabetic ketoacidosis

Background: Gastric cancer is the fifth most common and third most deadly cancer globally. It has three subtypes: intestinal, diffuse, and mixed, with intestinal being the most common. About 30% of gastric adenocarcinomas are diffuse (DGC). Although overall gastric cancer rates have declined due to H. pylori eradication and lifestyle changes, DGC incidence is rising. Risk factors include H. pylori infection, tobacco use, obesity, diet, and genetics. Around 1-3% of DGC cases are hereditary (HDGC), typically diagnosed before age 40, while non-hereditary DGC has a median diagnosis age of 70. DGC is most common in male Asians, Eastern Europeans, and South Americans. Over 40% of DGC patients present with metastatic disease, and the 5-year survival rate is 75% for localized disease, but only 7% for metastatic cases. DGC typically presents with abdominal pain, nausea, weight loss, and dysphagia. Histologically, it often features "signet ring" cells. The CDH1 mutation is most common, leading to reduced E-Cadherin expression, which promotes cancer spread.