Surgical margin assessment
Margin assessment for cancer resection specimens. Use the RCPA/ICCR dataset (CAP protocol in the US) for the tumour site.
All Pathways
PathologyDiagnostic
Surgical Margin Assessment Protocol (CAP)
Surgical Margin Assessment Protocol (CAP): Surgical margin assessment → Specimen orientation → Margin inking → Margin sampling → Microscopic evaluation.
Pathway Overview
12 steps
Algorithm Steps
12 total
01Start 02Action Specimen orientation
Orientation is needed to name each margin. Document it in the report.
- Record orienting sutures or clips and the surgeon's orientation
- Correlate with the request form and operative note
- Orientation unclear: contact the surgeon before inking
- Photograph or diagram the specimen before sectioning
03Action Margin inking
Ink each margin in a different colour before sectioning. Colorectal: the serosa (visceral peritoneum) is not a surgical margin; tumour there is pT4a, not an involved margin.
- Record the ink colour for each margin in the report
- Apply ink carefully: ink can track into clefts and mimic the true margin
- Let the ink dry before sectioning
04Action Margin sampling
Perpendicular sections give a distance. Shave (en face) sections do not: any tumour in a shave section means an involved margin.
- Take perpendicular sections where tumour is closest to the inked margin
- Shave (en face) margin: any tumour in the section = involved; report no distance
- Take extra sections where tumour is grossly close to a margin
- Separately submitted margins count in the final margin status
- Record which blocks show which margin
05Action Microscopic evaluation
Measure the distance from tumour to the nearest inked margin in mm. Fragmented specimen: state that margins cannot be assessed.
- Measure invasive carcinoma and in situ disease (or high-grade dysplasia) separately
- Name the closest margin(s)
- Colorectal: record to 0.1 mm if under 1 mm, and to 1 mm if under 10 mm
- State cautery or processing artefact that limits the measurement
06Warning Use site-specific margin definitions
No single mm cut-off applies to all sites. Use the dataset for the tumour site. Shave (en face) margin: any tumour = involved. Give the distance in mm where it can be measured. Colorectal serosa is not a margin: serosal tumour is pT4a, not an involved margin.
- Colorectal: circumferential (non-peritonealised) margin 1 mm or less = involved. Tumour in a node with intact capsule at the margin = not involved; add a comment
- Oral cavity SCC: under 1 mm involved; 1 to 5 mm close; over 5 mm clear
- Breast: involved = invasive carcinoma or DCIS at ink. Pure DCIS: SSO-ASTRO-ASCO adequate width is 2 mm (with whole-breast RT). After neoadjuvant therapy: use the post-neoadjuvant dataset
07Decision Margin category (site-specific)
Categorise with the site definition. Give the distance in mm for every category.
- Involved (site definition)
08Warning Involved margin: tumour at ink or within the site's involved distance
Report the margin as involved. Name each involved margin.
- State the tumour type at the margin: invasive or in situ
- Breast: extent at margin: unifocal (under 5 mm), multifocal or extensive (5 mm or more)
- Colorectal: involvement by a discontinuous deposit is reported as such, with its distance and the primary tumour's distance
09Action Margin report (synoptic): final step
Use the RCPA structured reporting protocol (ICCR-based) for the tumour site. Re-excision and adjuvant therapy are MDT decisions, not part of the margin report.
- Status for invasive and in situ disease: involved or not involved, with the site category
- Distance in mm to the closest margin, and which margin
- Each involved margin named, with extent where the dataset asks for it
- Method: perpendicular sections, shave margins or separate cavity margins
- Not assessable (for example fragmented specimen): state why
- Close (site definition)
10Action Close margin: not involved, but within the site's close range
Only some sites define a close range (for example oral cavity SCC 1 to 5 mm). Give the exact distance in mm.
- Report the exact distance in mm and name the closest margin
- If the site dataset has no close category, report the distance only
- Breast pure DCIS (or DCIS with microinvasion): state if the distance is under 2 mm
- Path rejoins step 09Shared downstream outcome
- Clear (site definition)
11Action Clear margin: beyond the site's involved and close ranges
Report the distance to the closest margin in mm and the site-specific category.
- Name the closest margin and give its distance in mm
- Give distances for invasive and in situ disease separately
- Breast pure DCIS (or DCIS with microinvasion): state if the distance is under 2 mm
- Do not write 'completely excised' without a distance
- Path rejoins step 09Shared downstream outcome
- Cannot be assessed
12Action Margins cannot be assessed: fragmented or distorted specimen
Report margin status as 'cannot be assessed' and state why. Do not give an involved, close or clear category.
- Give the reason: fragmented or piecemeal specimen, disrupted or unorientated surface, or severe cautery artefact
- If a margin is still identifiable, report its distance in mm and name it
- Path rejoins step 09Shared downstream outcome
Guideline Source
ICCR site-specific cancer datasets (adopted by RCPA structured reporting protocols; CAP cancer protocols in the US)
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- No single mm cut-off applies to all sites: use the RCPA/ICCR (or CAP) dataset for the tumour site.
- The margin report gives distance and category; re-excision and adjuvant therapy are MDT decisions.
- Shave (en face) margins give no distance.
- Fragmented specimens: margins cannot be assessed.
- Ex vivo flattening and ink tracking can make margins look narrower than in vivo.
Contraindicated Populations
Fragmented or piecemeal specimens (margins cannot be assessed)Mohs micrographic surgery (separate frozen-section margin method)
Applicable Regions
USAUUKEU
AU: Use the RCPA structured reporting protocol for the tumour site (ICCR-based).
UK: Use the RCPath cancer dataset for the tumour site.
US: Use the CAP cancer protocol template for the tumour site.
Version 2Next review: 2027-09-30
Next steps
Finish the workflow by opening the most relevant calculator, then convert the session into a live account when you are ready.
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 ICCR site-specific cancer datasets (adopted by RCPA structured reporting protocols; CAP cancer protocols in the US).
What guideline is the Surgical Margin Assessment Protocol (CAP) based on?
This algorithm is based on ICCR site-specific cancer datasets (adopted by RCPA structured reporting protocols; CAP cancer protocols in the US).
What are the limitations of the Surgical Margin Assessment Protocol (CAP)?
Known limitations include: No single mm cut-off applies to all sites: use the RCPA/ICCR (or CAP) dataset for the tumour site.; The margin report gives distance and category; re-excision and adjuvant therapy are MDT decisions.; Shave (en face) margins give no distance.; Fragmented specimens: margins cannot be assessed.; Ex vivo flattening and ink tracking can make margins look narrower than in vivo.. Individual patient factors may require deviation from these recommendations.
Get AI-Powered Analysis Alongside This Algorithm
In AttendMe.ai, the Surgical Margin Assessment Protocol (CAP) appears automatically when your clinical question matches — alongside evidence from 3M+ peer-reviewed articles.
Try AttendMe Free