Margin Assessment
Systematic approach to surgical margins
All Pathways
PathologyDiagnostic
Surgical Margin Assessment Protocol (CAP)
Surgical Margin Assessment Protocol (CAP): Margin Assessment → Specimen Orientation → Margin Inking → Margin Sampling → Microscopic Evaluation.
Pathway Overview
9 steps
Algorithm Steps
9 total
01Start 02Action Specimen Orientation
Essential for margin identification
- Receive fresh or fixed with surgeon orientation
- Document orienting sutures/clips
- Photograph before sectioning
- Correlate with surgeon operative note
- Contact surgeon if orientation unclear
03Action Margin Inking
Color-code margins
- Use multiple colors for different margins
- Document inking scheme
- Let ink dry before sectioning
- Consider agar to prevent smearing
- Standard protocol: anterior, posterior, superior, etc.
04Action Margin Sampling
Adequate representation
- Perpendicular sections show true distance
- Shave margins for large specimens
- Sample closest margin to tumor
- Additional sections if grossly close
- Document sections submitted per margin
05Decision Microscopic Evaluation
Assess tumor to margin distance
- Identify inked margin on slide
- Measure tumor to margin (mm)
- Note invasive vs in situ at margin
- Assess for LVI near margin
06Warning Positive Margin
Tumor at inked surface
- Tumor cells touching ink
- Specify which margin(s) positive
- Note extent (focal vs extensive)
- Invasive vs in situ if applicable
- Clinical significance: re-excision often needed
07Action Margin Reporting
Synoptic elements
- Status: Positive/Close/Negative
- Distance in mm for closest margin
- Which margin(s) involved
- Invasive vs in situ component
- Extent if positive (focal/extensive)
08Action Close Margin
Tumor near but not at margin
- Breast: <2mm often considered close
- Head/neck: <5mm often close
- Report exact distance in mm
- Site-specific and context-specific definitions
- May trigger re-excision or boost radiation
- Path rejoins step 07Shared downstream outcome
09Outcome Negative Margin
Adequate clearance
- Tumor well away from inked surface
- Report distance to closest margin
- No re-excision typically needed
- Site-specific adequacy (1mm vs 10mm)
- Document which margins negative
- Path rejoins step 07Shared downstream outcome
Guideline Source
CAP Cancer Protocol Templates - Margin Evaluation
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- Margin definitions vary by tumor type
- Inking and orientation critical
- Cannot assess margins on fragmented specimens
- Close margin definitions institution-specific
- Re-excision criteria vary
Applicable Regions
USAUUKEU
AU: RCPA structured reporting
UK: RCPath minimum dataset
US: CAP protocol requirements
Version 1Next review: 2027-01-01
Next steps
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Related Resources
Frequently Asked Questions
What is the Surgical Margin Assessment Protocol (CAP)?
The Surgical Margin Assessment Protocol (CAP) is a diagnostic clinical algorithm for Pathology. It provides a structured decision tree to guide clinical decision-making, based on CAP Cancer Protocol Templates - Margin Evaluation.
What guideline is the Surgical Margin Assessment Protocol (CAP) based on?
This algorithm is based on CAP Cancer Protocol Templates - Margin Evaluation (DOI: 10.5858/arpa.2020-0024-SA).
What are the limitations of the Surgical Margin Assessment Protocol (CAP)?
Known limitations include: Margin definitions vary by tumor type; Inking and orientation critical; Cannot assess margins on fragmented specimens; Close margin definitions institution-specific; Re-excision criteria vary. Individual patient factors may require deviation from these recommendations.
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