E4820. Through the Lens: Imaging Insights Into Gastric Adenocarcinoma
  1. Annie Huang; David Geffen School of Medicine at UCLA
  2. Karoly Viragh; Olive View UCLA Medical Center
  3. Priyanka Dube; Olive View UCLA Medical Center
  4. Mariam Thomas; Olive View UCLA Medical Center
  5. Shawdi Manouchehr-Pour; Olive View UCLA Medical Center
Gastric adenocarcinoma (GAC) is the most common type of gastric malignancy and one of the leading causes of cancer-related deaths. While overall incidence and mortality rates from GAC in the United States have been declining, GAC continues to be a pressing health concern within rapidly expanding Hispanic and Asian communities. Contributing factors include H pylori infection, diet, and socioeconomic background within these populations. Despite the lack of gastric cancer screening recommendations, the stomach is included on nearly all thoracoabdominal imaging examinations due to its central location, providing an opportunity for evaluation. Although endoscopy remains the gold standard for diagnosis of GAC, oftentimes gastric masses are incidentally found on CT scans performed for epigastric pain or other indications. Additionally, CT serves as initial staging modality once GAC is diagnosed. It is imperative to understand clinical challenges and diagnostic pitfalls to maximize the chances of early cancer detection.

Educational Goals / Teaching Points
The goal of the current educational exhibit is to (1) offer a comprehensive overview of GAC, encompassing diagnosis, staging, and management; (2) describe the roles of dedicated imaging techniques should an abnormality be suspected on routine imaging; and (3) illustrate both common and uncommon presentations of GAC through cases from a high-volume safety net county hospital serving a large metropolitan area.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The strengths and limitations of various imaging techniques used to diagnose GAC are detailed in the current educational exhibit. Fluoroscopy is a low-cost screening technique that can provide detailed evaluation of the gastric mucosa in patients presenting with symptoms concerning for GAC. We describe various appearances of GAC on fluoroscopy and their corresponding cross-sectional imaging findings. While limited in detecting early GAC, CT imaging is useful for initial staging and identifying distant metastasis. Subtle findings of incidental GAC can be easily missed on CT due to suboptimal distension of the stomach and lack of contrast administration. MRI is not often used for staging GAC due to time and cost; however, it limits radiation, offers better soft tissue resolution, and can further characterize indeterminate metastatic lesions. PET/CT is useful for detecting distant metastases but can result in false positives in settings of inflammation and infection. Select cases illustrate concepts such as incidental intraabdominal findings on chest CT or uncommon metastatic patterns such as leptomeningeal disease.

In conclusion, recognition of characteristic findings of GAC is crucial as GAC is often incidentally identified. In this exhibit, we review gastric anatomy, demographics, and histopathologic background of GAC, imaging techniques, and various imaging presentations of GAC. Cases have been chosen to impart practical insights, diagnostic pitfalls, and/or highlight important concepts, such as various metastasis and complications. Surgical, pathological, and clinical correlation are provided when available.