The short answer
Melanoma decisions are built on one measurement, the Breslow thickness in millimeters. It sets the surgical margin and the 0.8 mm line for node sampling, and a positive node no longer means removing all the rest.
Breslow thickness, the depth of the melanoma in millimeters, is more reproducible than the older Clark level and should always be reported.
Localized melanoma is removed with margins proportional to the microstage, so a thicker lesion gets a wider margin.
Sentinel lymph node biopsy should be considered for primary tumors at least 0.8 mm thick when the nodes feel normal, and for thinner ulcerated ones with other bad features.
After a positive sentinel node, complete dissection did not improve distant metastasis-free survival, and lymphedema occurred in 24.1% against 6.3% of those observed.
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The full explanation.
Start with the thickness on your report
Melanoma decisions are built on one measurement. NCI calls it the Breslow thickness, the depth of the melanoma in millimeters.
NCI says it is more reproducible than the older Clark level, and predicts behavior better in lesions thicker than 1.5 mm. It should always be reported.
Ask for the number. Ask whether the report says ulcerated.
How wide the surgery goes
NCI describes surgical excision as the main treatment for melanoma that has not spread. It says localized melanoma is removed with margins proportional to the microstage of the lesion.
In plain terms, a thicker melanoma gets a wider margin. Ask what margin is planned for you, and whether a graft or flap will be needed.
The 0.8 mm threshold for node sampling
NCI is specific here. Sentinel lymph node biopsy should be considered for primary tumors at least 0.8 mm thick, when the nodes feel normal.
It adds that thin melanomas under 0.8 mm that are ulcerated may also warrant it, especially with other bad features.
Ask whether you cross that line, and what a positive node would change.
If a sentinel node is positive
Removing all the nodes was once the automatic next step. NCI reports trial data that changed this.
Complete node dissection did not improve distant metastasis-free survival. Lymphedema occurred in 24.1% of the dissection group, against 6.3% of those observed.
No subgroup was found that clearly benefited from the larger operation. NCI describes ultrasound surveillance of the regional nodes instead.
Treatment after surgery
NCI says adjuvant options are expanding for people at high risk of recurrence after complete removal.
It notes that resected stage IIB and IIC melanoma carries a similar risk of recurrence and death as stage III, even without node involvement.
NCI also describes neoadjuvant pembrolizumab, given before surgery, for high-risk node-positive or resectable metastatic disease. In one trial that approach improved event-free survival.
Questions to ask before surgery
- What is my Breslow thickness, and is my melanoma ulcerated?
- How wide a margin are you taking, and will I need a graft?
- Do I need a sentinel lymph node biopsy?
- If a node is positive, will you remove the rest or watch them with ultrasound?
- Should my tumor be BRAF-tested now, even before drugs are discussed?
- Am I stage IIB or IIC, and does adjuvant treatment apply to me?
- Is treatment before surgery an option in my case?
Ask about trials early
NCI notes that melanoma drugs and combinations are arriving quickly. It says taking part in trials is an important option for all patients at high risk.
That is an unusually direct statement. Ask what is open where you are treated.
Related pages
Next: Cancer Staging, Biomarker Testing, Clinical Trial vs Standard Treatment, and Questions to Ask Your Doctor.
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Words to know
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Common questions
Which number on my pathology report matters most?
The Breslow thickness, the depth in millimeters. Ask for that number and whether the report says ulcerated. Margin width and node sampling both follow from it.
Do I need a sentinel lymph node biopsy?
It should be considered at 0.8 mm or thicker when the nodes feel normal. Thin ulcerated melanomas under 0.8 mm may also warrant it. Ask what a positive node would change.
If a node is positive, will the rest be removed?
Not automatically. Complete dissection did not improve distant metastasis-free survival, and no subgroup clearly benefited. NCI describes ultrasound surveillance of the regional nodes instead.
Should I ask about a clinical trial early?
Yes. NCI notes that melanoma drugs and combinations are arriving quickly, and says taking part in trials is an important option for all patients at high risk.
Questions to ask your doctor
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Sources last checked: 2026-07-30 what this meansLast updated: 2026-08-16Next planned review: 2027-07-30
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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