Surgical Margins
- Abbie Tipler
- Dec 12
- 3 min read
This blog post is a summary of the key take-home points for a talk I gave on surgical margins. I was inspired to give the talk, after finding this fabulous, free to access paper with the best images titled:Fascial Plane Mapping for Superficial Tumor Resection in Dogs
it can be found by following this link.
It is an anatomical study aimed at improving surgical planning for oncologic resections by categorising fascial planes in the canine neck and trunk. The paper maps fascial plane anatomy relevant to superficial tumour resections in dogs. This provides the information that can guide surgeons in identifying the appropriate deep surgical plane.
When we say 'X lateral margin, and 1 fascial plane deep - the deep fascial plane is what represents the deep 'natural' barrier. It can be actual fascia itself, or it can also be epimysium of the muscle. There is no point getting a great '2-3cm' lateral margin, and failing to achieve a deep one. This study helps you visualise the anatomy - I love it!
Secondly re margins, is ensuring you get the most information from your pathologist.
The following summarises the pathology part of the talk, that I gave with Specialist Pathologist Louise Sullivan (from QML).
1. Getting the Specimen Right: Handling & Submission
Fixation
Place samples in 10% neutral buffered formalin immediately after excision. If using surgical ink, apply it before immersion. Use wide-mouthed, leak-proof plastic containers and clearly label with patient name and anatomical site.
Multiple specimens
Submit each lesion separately. If that’s not possible, differentiate with inks, sutures, or clear descriptors. Keep cytology samples well away from formalin fumes.
Formalin volume
Use a 1:10 tissue-to-formalin ratio. Small samples go into cassettes; very large ones can be bread-loafed without cutting into margins. When unsure, contact your laboratory.
2. Clinical Information Matters
Always include:
Signalment
Relevant history and comorbidities
Detailed lesion description (size, location, behaviour)
Imaging results
Clinical photos or radiographs (email if needed)
Clinical context is essential. If histopathology does not match your clinical impression, contact the pathologist for clarification or further assessment.
3. Specimen Size and Sampling Limitations
Small samples (punch or needle biopsies) may:
Miss diagnostic tissue
Underrepresent tumour grade
Mischaracterise tumour type
Large samples Only representative sections can be examined, so margin assessment never captures the entire surgical edge.
4. Histologic Margin Evaluation: Strengths and Limitations
Margin evaluation is important for curative-intent surgery, but keep in mind:
The true margin exists in the patient.
The surgical margin is created by the surgeon.
The histologic margin is created during trimming and processing.
Tissue shrinkage and distortion can alter tumour-free distances. Histologic margins do not reliably predict recurrence—tumour biology remains the dominant driver.
5. Optimising Margin Accuracy
Clearly indicate whether margin assessment is required.
Do not incise the surgical edge after excision; this creates distortion.
When gross margins are uncertain, tumour bed samples can be submitted separately.
6. Marking Your Margins: Ink and Sutures
Ink is preferred.
Apply surgical ink before fixation, using different colours to identify specific margins (document on the submission form).
How to apply ink:
Blot the tissue dry.
Dab (do not dip) with a swab or sponge.
Allow to dry before placing in formalin.
Poorly applied ink can track into tissue planes and produce artefacts. Sutures can help with orientation but are less reliable than ink for defining true edges.
7. Trimming and Reporting: What to Expect
Radial (cross-section) trimming is commonly used but samples only a small portion of the margins.Reports for malignant tumours should describe:
The tumour’s relationship to surrounding tissues
The histologic tumour-free distance to the closest margin
Any fascial planes or barriers involved
Avoid relying on subjective terms like “clean,” “dirty,” or “narrow”; instead interpret exact measurements alongside tumour behaviour and grade.
Take-Home Messages
Good histopathology depends on good surgery, good handling, and good communication with your pathologist
Margin status is valuable but should always be interpreted in context.
Inking margins before fixation significantly improves diagnostic accuracy.
If histology does not align with the clinical picture, discuss the case with your pathologist.
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