What is the diagnostic approach for adenocarcinoma of the stomach?

Diagnostic Approach for Adenocarcinoma of the Stomach

Histopathological examination is the gold standard for diagnosing gastric adenocarcinoma and must be performed prior to initiating any treatment. 1

Initial Diagnostic Evaluation

Endoscopy and Biopsy

• Perform gastroscopic examination with multiple biopsies (5-8 samples) to provide adequate material for histological interpretation 1
• Target suspicious areas using narrow-band imaging or chromoendoscopy with magnifying endoscopy for better visualization 1
• Ensure biopsy specimens are reviewed by an experienced pathologist according to WHO criteria 1
• When repeated gastroscopic biopsies are inconclusive, consider cytological examination of ascites/pleural effusion or biopsy of metastatic lesions 1

Blood Tests

• Complete blood count (check for iron-deficiency anemia)
• Liver and renal function tests
• Consider alpha-fetoprotein (AFP) measurement, as elevated levels may be present in some gastric adenocarcinomas 2

Imaging for Staging

Computed Tomography (CT)

• Thoracic, abdominal, and pelvic CT with contrast is the primary diagnostic modality for pre-treatment clinical staging 1
• Use multiphase and multi-planar enhanced contrast scan (plain abdominal CT scans are not recommended) 1
• Patient preparation: Ensure gastric cavity is fully dilated by drinking 500 mL of water prior to examination 1
• CT helps detect:
  • Local tumor extension
  • Regional lymphadenopathy
  • Distant metastases

Endoscopic Ultrasound (EUS)

• Recommended as the preferred cT staging modality for evaluating depth of tumor invasion 1
• Particularly valuable for:
  • Determining proximal and distal extent of the tumor
  • Visualizing different anatomical layers of the gastric wall
  • Detecting enlarged perigastric lymph nodes
  • Identifying metastatic lesions in neighboring liver and peritoneal cavity 1
• EUS has high sensitivity and specificity in distinguishing between different T stages:
  • Between T1/2 and T3/4: sensitivity 0.86, specificity 0.90
  • Between T1 and T2: sensitivity 0.85, specificity 0.90
  • Between T1a and T1b: sensitivity 0.87, specificity 0.75 1

Additional Imaging Studies

• MRI: Consider when liver metastasis is suspected on CT scan; hepatocyte-specific contrast agents can increase diagnostic sensitivity 1
• PET/CT: May improve staging through increased detection of involved lymph nodes and metastatic disease, though may be less useful in mucinous tumors 1

Surgical Staging

• Diagnostic laparoscopy with peritoneal washings is recommended for detecting occult metastasis and when peritoneal metastasis is suspected 1
• For intraperitoneal lavage, infuse 200 mL of normal saline into different quadrants of the abdominal cavity and collect >50 mL for cytological examination 1

Histopathological Classification

• Classify according to WHO criteria and Lauren classification (intestinal, diffuse, or mixed types) 1
• Assess HER2 status in all cases of gastric or esophagogastric junction adenocarcinoma for potential targeted therapy 1

Common Pitfalls to Avoid

1. Inadequate biopsy sampling: Ensure multiple biopsies (5-8) are taken, especially in ulcerated lesions
2. Improper CT technique: Always use contrast enhancement and ensure adequate gastric distension
3. Overlooking peritoneal metastases: Consider diagnostic laparoscopy in all stage IB-III gastric cancers
4. Missing hereditary syndromes: Consider genetic testing in patients with family history or early-onset disease
5. Neglecting HER2 testing: Essential for all gastric adenocarcinomas to determine treatment options

Special Considerations

• For suspected carcinoma of the esophagogastric junction, enhanced CT scan of the chest should be performed to assess mediastinal lymph nodes 1
• In patients with suspected hereditary gastric cancer syndrome (e.g., hereditary diffuse gastric cancer, Lynch syndrome), refer to a genetics specialist 1

By following this systematic diagnostic approach, clinicians can ensure accurate diagnosis and staging of gastric adenocarcinoma, which is crucial for determining appropriate treatment strategies and improving patient outcomes.