Medical Oncologist
CION Cancer Clinics
How wide is 'wide'? Margins by cancer type | CION Cancer Clinics
A wide excision margin is not one fixed number. It runs from a few millimetres for a small basal cell skin cancer, to 1 cm or 2 cm for melanoma depending on its depth, to a cuff of muscle for a soft tissue sarcoma. The width is set by the cancer type and how deep it grew, not by the size of the lump. This page gives the usual ranges and explains why wider is not safer. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- How many centimetres is a "wide" margin?
- What is the usual margin for each cancer type?
- Why not just take more to be safe?
- How is the margin decided for you?
- What can make your margin bigger or smaller than the table?
- Margin words on the pathology report, in plain language
- Four things families tell us about margins, and what is true
- Common questions about excision margins
The short answer
How many centimetres is a "wide" margin?
There is no single number. A wide margin, the rim of healthy tissue taken around a cancer, ranges from a few millimetres for a small basal cell skin cancer to 2 cm for a thick melanoma, and to a cuff of muscle for a sarcoma. The figure is set by the type of cancer and how deep it has grown, not by the size of the lump you can see.
Why the number changes with the cancer
Different cancers spread outward in different ways. A basal cell cancer creeps slowly and rarely sends cells far from its edge, so a small rim is enough. Melanoma can seed tiny groups of cells in the skin around it, and the deeper it has grown, the further those cells may sit. A sarcoma pushes a false capsule ahead of itself, with cancer cells often just outside it, so the surgeon takes a cuff of normal tissue rather than shelling the lump out.
Measured where, exactly?
The margin drawn on your skin and the margin on the pathology report are two different measurements. The first is what the surgeon plans. The second is the distance the laboratory measured from the nearest cancer cell to the cut edge, after the tissue has shrunk in preserving fluid. The second number is always smaller, and that is expected.
Side by side
What is the usual margin for each cancer type?
These are the guideline ranges most teams work from. Your own margin may sit outside them for reasons your surgeon can explain.
Cancer type
Typical planned margin
Melanoma in situ (in the top layer only)
0.5 cm to 1 cm of skin around the scar
Melanoma up to 1 mm thick
1 cm
Melanoma 1 mm to 2 mm thick
1 cm to 2 cm, depending on the site
Melanoma thicker than 2 mm
2 cm
Basal cell and squamous cell skin cancer
A few millimetres, more for higher-risk ones
Breast lump (lumpectomy)
No cancer at the inked edge; slightly more for DCIS
Soft tissue sarcoma
A cuff of normal tissue, or a natural barrier such as muscle covering
Not sure whether this applies to you?
Ask an oncologistA fair question
Why not just take more to be safe?
Because past a certain width, extra tissue does not add protection. For melanoma, large trials compared narrower and wider margins and found that going beyond the guideline width did not lower the chance of the cancer returning. It did leave people with bigger wounds, more skin grafts and more problems with movement.
What a wider cut costs the patient
Every extra centimetre has to be closed. Up to a point the skin stretches and the wound is stitched edge to edge. Past that point the surgeon needs a skin graft or a flap: a second wound, longer healing and a more visible result. Near a joint, an extra centimetre can mean a scar that pulls when you bend. On the face, it can pull the corner of the eye or the mouth.
When a smaller margin is deliberately chosen
On the ear, the nose, an eyelid, a finger or the genitals, the guideline width is sometimes not possible without losing function. In those places your surgeon may plan a narrower margin and check the edges more carefully, or suggest radiotherapy instead. This is a considered trade, not a shortcut.
Ask: "What margin are you planning, and what would change your mind about it?" Both halves matter.The pathway
How is the margin decided for you?
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The biopsy report
The tissue from the first removal tells the team the cancer type and, for melanoma, how deep it went in millimetres. That single depth figure sets the width of the second operation.
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Looking at the site
The surgeon examines where the scar sits, how loose the skin is around it, and what lies underneath. The same cancer on the back and on the shin gets the same planned margin but a very different closure.
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Tumour board
Cases that are unusual, deep or in a difficult place are discussed by surgical, medical and radiation oncologists together, so the margin and any treatment after surgery are planned as one.
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Drawing it on the skin
On the day, the planned width is measured out with a ruler and drawn around the scar before anything is numbed. Ask to see it.
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The laboratory checks
After the operation, the pathologist measures the real distance from cancer to cut edge. If it is too close or involved, a small second operation or radiotherapy is discussed.
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The variables
What can make your margin bigger or smaller than the table?
Depth and grade
For melanoma, depth is everything. For other skin cancers, a higher grade, meaning cells that look more abnormal, or growth along a nerve pushes it up.
Where it sits
Tight skin over the shin, the scalp or the hand cannot give what the back can. The planned width may be kept but the closure changes, or the width is trimmed and the edges are checked more closely.
Sites that often need a compromise
- Nose, ear and eyelid
- Fingers and toes
- Over a joint
A previous operation
If the first removal took a wide edge already, or if a cancer has come back in an old scar, the surgeon plans from the scar rather than from a fresh lump, and often takes more.
Treatment planned afterwards
Where radiotherapy will follow, as it often does for sarcoma and for breast cancer, the team may accept a slightly closer margin rather than remove a large amount of healthy tissue.
A joint decision made before the operation, not an excuse afterwards.On your report
Margin words on the pathology report, in plain language
- Peripheral margin
- The distance from the cancer to the cut edge at the sides. The report usually gives the closest one in millimetres.
- Deep margin
- The distance to the underside of the piece removed. Often the tighter of the two, because there is only so much depth to take.
- Breslow thickness
- For melanoma, how deep the cancer grew, measured in millimetres from the skin surface. This is the number that set your margin.
- Clear, close, involved
- Clear means no cancer at the edge. Close means near it. Involved means cancer reaches the edge and more treatment is usually discussed.
- Inked margin
- The laboratory paints the outside of the piece before cutting it, so that under the microscope the true edge is unmistakable.
Commonly believed
Four things families tell us about margins, and what is true
"The lump was tiny, so the operation should be tiny."
The margin is set by cancer type and depth, not by the size of what you could see. A small but deep melanoma needs a wider rim than a large but shallow basal cell cancer.
"The report says 3 mm but the surgeon promised 1 cm."
Tissue shrinks once it is removed and preserved, and the laboratory measures from the nearest cancer cell rather than from the scar. A smaller figure on the report is normal. What matters is whether the margin is called clear.
"A wider margin means the cancer is worse."
It means the guideline for that type and depth calls for it. A 2 cm margin is standard for a thicker melanoma and says nothing further about outlook on its own.
"A close margin means the surgeon made a mistake."
Close margins happen when the cancer extended further under the skin than anyone could see, or when function had to be protected. They are dealt with by a small further operation or radiotherapy, and they are common.
Questions we are asked
Common questions about excision margins
Is 1 cm really enough for a melanoma?
For a melanoma up to 1 mm thick, yes, that is the width trials and guidelines support. Wider cuts were tested and did not lower the chance of the cancer coming back in that spot. If your melanoma is thicker, the plan will be wider.
How deep does the surgeon go?
For skin cancers, through the full thickness of the skin and the fat beneath it, usually down to the sheet of tissue covering the muscle. For a sarcoma, the depth is planned from the MRI and may include part of a muscle.
Why is the scar so much longer than the margin?
A round hole does not close flat. The surgeon removes an oval roughly three times as long as it is wide so the two edges meet without puckering. A 1 cm margin around a small scar can therefore leave a line several centimetres long.
Can the margin be checked during the operation?
Sometimes. Frozen section, a quick check of a sliver of tissue while you are still on the table, is used in some centres for certain cancers. Mohs surgery does this for every edge, layer by layer. Neither is routine for melanoma.
What does "margin not assessable" mean?
The laboratory could not measure one edge, usually because the tissue arrived in pieces or the sample was small. It does not mean cancer was found there. Your team will decide whether to accept it, re-excise, or watch the area.
Do margins matter as much if I am having radiotherapy?
They still matter, but radiotherapy changes the calculation. For breast cancer and sarcoma the team may accept a closer margin because radiotherapy will treat the area anyway. That decision is made with the whole team, and you should hear it explained rather than discover it on a report.
Can I ask for a smaller margin because of the scar?
You can ask, and on the face your surgeon may already be planning one with closer checking of the edges. Elsewhere, a margin below the guideline raises the chance of the cancer returning locally, and a second operation then usually leaves a bigger scar than the first would have.
What is the margin for cancers this page has not listed?
Rarer skin cancers such as Merkel cell and dermatofibrosarcoma have their own guideline widths, often wider than for common skin cancers. Cancers inside the body follow organ-specific rules. If your report names something not covered here, call the helpline with the report.
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Dr. C. Raghavendra Reddy
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
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Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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Sources
- NICE — Melanoma: assessment and management (NG14)
- National Cancer Institute — Melanoma Treatment (PDQ) - Patient Version
- Cancer Research UK — Surgery for melanoma skin cancer
- American Cancer Society — Surgery for Basal and Squamous Cell Skin Cancers
- Cancer Research UK — Surgery for soft tissue sarcoma
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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Wide Local Excision: What It MeansThe operation itself, explained from the startWide Excision for MelanomaDepth, margins and the sentinel node, in one placeWide Excision for Soft Tissue SarcomaWhy sarcoma margins are measured in tissue layers, not centimetresRe-Excision When Margins Are PositiveWhat happens when the report says involved or closeThe Pathology Report After SurgeryReading the rest of the report
Talk to us
Not sure what margin is being planned for you?
Send us the biopsy report or call the helpline. A surgical oncologist will explain which guideline width applies to your cancer and what to ask your surgeon. One helpline serves every CION centre.