Excision Margins in Melanoma

Article:

Farooq MS, Manahil Haider Jeoffrey S, Vargas GM, Karakousis GC. Margins for Melanoma: Extent of Resection, Alternative Approaches, and Future Considerations.   Surg Oncol Clin N Am. 2025 Jul;34(3):297-318

Understanding Surgical Margins for Melanoma

When melanoma is diagnosed, your surgeon must remove the tumor along with some surrounding healthy skin—this border of healthy tissue is called the surgical margin. Getting the margin right is critical: too narrow and cancer cells might be left behind; too wide and you face larger scars, more difficult healing, and potentially needing skin grafts.

How Doctors Decide on Margin Size

The main factor determining your margin size is how deep the melanoma has grown into your skin, measured in millimeters (called Breslow thickness). Current guidelines recommend:

- Melanoma in situ (confined to top skin layer): 0.5–1 cm margin

- Thin melanoma (less than 1 mm deep): 1 cm margin 

- Intermediate melanoma (1–2 mm deep): 1–2 cm margin

- Thick melanoma (over 2 mm deep): 2 cm margin

These recommendations come from seven major clinical trials conducted over 30+ years involving thousands of patients. Early guidelines in the 1900s called for removing 5 cm of skin around melanomas, but decades of research proved that narrower margins are just as safe and cause far less scarring and complications.

The Standard Approach: Wide Local Excision

Wide local excision (WLE) is the gold-standard surgery for melanoma. Your surgeon removes the melanoma plus the recommended margin of normal-appearing skin in an elliptical (football) shape, going down through the fat layer. The wound is typically closed with stitches, though larger removals may require skin grafts or tissue rearrangement.

Studies show that using a 1–2 cm margin for most melanomas results in very low rates of the cancer coming back at the surgery site (less than 1–2%), with excellent long-term survival and fewer complications than older, more aggressive surgeries.

An Alternative: Mohs Surgery

Mohs micrographic surgery is a specialized technique where the surgeon removes thin layers of skin one at a time, examining each layer under the microscope immediately to check for cancer cells, and continues until margins are clear.

Mohs offers two potential advantages: it examines 100% of the margin (versus small samples in standard pathology), and it can spare healthy tissue in cosmetically sensitive areas like the face or functionally important areas like fingers. Studies show Mohs achieves very low recurrence rates (often under 1%) for melanoma, especially for certain types like lentigo maligna on the face.

However, Mohs is not currently the standard of care for most melanomas because no head-to-head randomized trials have compared it directly to WLE, and most existing studies have limitations—Mohs has mainly been used for thinner, lower-risk melanomas, making it hard to compare results. National guidelines recommend Mohs only for select thin melanomas in areas where standard margins would cause unacceptable cosmetic or functional problems.

Special Situations

Some melanoma types require different approaches:

- Lentigo maligna (a flat melanoma often on sun-damaged face/neck skin) may need wider margins (9–15 mm) because it spreads unpredictably beyond visible borders 

- Acral melanoma (on palms, soles, or under nails) historically required amputation of fingers/toes, but newer techniques preserving function are being studied

- Melanoma in situ on the trunk/arms/legs can often be cleared with just a 5 mm margin

Take Home Message:

If you're diagnosed with melanoma:

1. Your pathology report will include Breslow thickness, ulceration status, and other factors your surgeon uses to plan margins

2. Most melanomas can be successfully removed with 1–2 cm margins, balancing complete removal with good cosmetic results

3. For melanoma on your face, hands, feet, or other challenging areas, ask your surgeon whether standard excision or specialized techniques like Mohs might be better for your situation

4. Even if margins are initially too narrow, additional surgery (re-excision) can clear remaining cancer cells

The good news: surgical cure rates for melanoma caught early are excellent, and ongoing research continues refining techniques to maximize both cancer control and quality of life after treatment.