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.

Case Presentation: A 77-year-old male with Type 2 diabetes, peripheral artery disease, heart failure, hyperlipidemia, benign prostate hypertrophy, and hypothyroidism presented with abdominal pain, nausea, and vomiting for 2 weeks, along with decreased mental status and missed insulin doses.

Physical exam showed dry mucous membranes, tachycardia, mild abdominal tenderness, and lethargy. Lab results: WBC 22.2, Na 118, K 7.3, BUN 70, Cr 2.8, Glucose 738, AG 30, pH 7.09. Differential diagnoses included DKA, mesenteric ischemia, and others.

CTA was negative for ischemia, but an abdominal CT revealed liver lesions, lymphadenopathy, and a past cholecystectomy. The patient was diagnosed with DKA and treated with fluids and insulin in the ICU. He developed Afib RVR, treated with amiodarone. An MRI showed pleural effusion, ascites, liver lesions, and gastroesophageal thickening. EGD biopsy confirmed diffuse gastric adenocarcinoma. After stabilization, he was transferred to a large medical institution for further oncological treatment.

Discussion: Gastrectomy is the first-line treatment for localized diffuse gastric adenocarcinoma (DGC). As cancer increases in size, spreads to lymph nodes/adjacent organs, radiation and chemotherapy are often employed. Additionally, depending on the stage of cancer, palliative care is an option. Advanced age in conjunction with abdominal pain, nausea, and vomiting is a common presentation for gastric cancer. What made this case unique was the recent history of insulin noncompliance and the presence of diabetic ketoacidosis. Due to the considerable overlap in symptomatology between these two conditions, without appropriate imaging it is likely that his underlying malignancy would have been missed. Additionally, while diabetes and hyperglycemia are associated with worse outcomes in gastric cancer, DKA is not associated with diffuse gastric carcinoma.