What Samples Collected During Endoscopy Are Tested For
Endoscopic biopsy samples are primarily tested for histopathologic diagnosis including detection of dysplasia, malignancy, inflammatory changes, and specific disease features, with the exact testing determined by the clinical indication for the procedure.
Primary Testing Based on Clinical Context
For Barrett's Esophagus Surveillance
When performing endoscopy for Barrett's esophagus, biopsies are systematically collected and tested for:
- Dysplasia grading (no dysplasia, low-grade dysplasia, high-grade dysplasia)
- Adenocarcinoma detection (intramucosal or invasive)
- Confirmation of Barrett's metaplasia (intestinal metaplasia with goblet cells)
The Seattle biopsy protocol should be followed: 4-quadrant biopsies every 2 cm for non-dysplastic Barrett's, or every 1 cm when dysplasia is known or suspected, plus targeted biopsies of any visible mucosal irregularities 1, 2. Each biopsy specimen is submitted separately to pathology and undergoes routine hematoxylin and eosin (H&E) staining for histologic evaluation 1.
For Inflammatory Bowel Disease
In suspected or established IBD, biopsies are tested for:
- Chronic inflammatory changes (architectural distortion, basal plasmacytosis, crypt abscesses)
- Disease activity assessment (acute inflammation, erosions, ulceration)
- Differentiation between ulcerative colitis and Crohn's disease
- Exclusion of other colitides (infectious, ischemic, medication-induced)
- Dysplasia surveillance in long-standing disease
Multiple biopsies from both visibly inflamed and normal-appearing mucosa are essential, as up to 25% of cases show histologic inflammation in endoscopically normal areas 3.
For Suspected Malignancy
When cancer is suspected (esophageal, gastric, or colorectal), biopsies are tested for:
- Histologic confirmation of malignancy (adenocarcinoma vs. squamous cell carcinoma)
- Tumor grade and differentiation
- Depth of invasion (when assessable from biopsy)
- Biomarker testing for precision oncology (HER2, microsatellite instability, PD-L1, etc.)
At least 6 biopsies should be obtained from suspected malignant lesions to ensure adequate tissue for both diagnosis and biomarker analysis 4. However, real-world data shows that 41-43% of procedures yield fewer biopsies than recommended, and only 50-67% of collected samples actually contain invasive carcinoma suitable for biomarker testing 4.
Advanced Testing Modalities
Tissue Systems Pathology Assays
For non-dysplastic Barrett's esophagus, tissue-based prediction assays (Tissue Cypher) may be utilized for risk stratification, analyzing 9 protein biomarkers plus nuclear morphology to predict progression risk to high-grade dysplasia or adenocarcinoma 2.
Wide-Area Transepithelial Sampling (WATS-3D)
WATS-3D may be used as an adjunctive technique in Barrett's surveillance, particularly for patients with indeterminate dysplasia or clinically high-risk non-dysplastic Barrett's esophagus. This brush-based sampling provides 3-dimensional tissue analysis with 7.2% incremental yield for dysplasia detection 2.
Molecular Biomarkers
Current guidelines recommend against routine use of molecular biomarkers to confirm dysplasia diagnosis or for risk stratification in Barrett's esophagus, as they have not been adequately validated 1.
Critical Caveats
Inflammation and Timing
When erosive esophagitis (Los Angeles Grade C or D) is present, biopsies may still be obtained if dysplasia or malignancy is suspected, but repeat endoscopy after 8 weeks of twice-daily PPI therapy is mandatory to confirm findings and avoid overcalling dysplasia in the setting of inflammation 2.
Sample Adequacy
The quality of histopathologic diagnosis depends critically on:
- Adequate number of biopsies (adherence to Seattle protocol increases dysplasia detection by 2.75-fold) 2
- Proper specimen handling (separate submission of targeted biopsies from mucosal irregularities) 1
- Sufficient tumor cellularity for biomarker testing (≥20% tumor cells for most molecular analyses) 4
What Is NOT Routinely Tested
- Immunohistochemistry or special stains are not needed routinely for IBD diagnosis 3
- Chromoendoscopy or advanced imaging is not required for routine Barrett's surveillance 1
- Microbial cultures are not performed on diagnostic biopsies (only on endoscope surveillance samples for quality control) 5, 6
The specific tests ordered depend entirely on the clinical indication documented at the time of endoscopy, emphasizing the importance of clear communication between endoscopist and pathologist 3.