The short answer
Melanoma staging looks at how thick the tumor is, whether it has ulceration, and whether it has reached lymph nodes or distant organs. Stages range from 0 (in situ) to IV (spread to distant parts of the body).
Melanoma staging is based mainly on tumor thickness, ulceration, and spread.
Stage 0 means the abnormal cells are only in the outer layer of skin.
Stages I and II describe melanoma that has not reached the lymph nodes.
Stage III means the cancer has reached nearby lymph nodes or skin.
Choose how you want to understand this
The full explanation.
The simple version
Staging describes how much melanoma is present and whether it has spread. It rests mainly on three things. One is how thick the tumor is. Another is whether the skin over it is broken, which is called ulceration. The third is whether the cancer has reached lymph nodes or distant organs. Stages run from 0 to IV.
What the stages mean
- Stage 0 (in situ). Abnormal cells sit only in the outer layer of skin, called the epidermis. They have not grown deeper.
- Stage I. A thin tumor, up to 2 millimeters thick, with no spread to lymph nodes. Stage IA is 1 millimeter or thinner, with or without ulceration. Stage IB is more than 1 but not more than 2 millimeters thick, without ulceration.
- Stage II. A thicker tumor, still with no spread to lymph nodes. It splits into IIA, IIB, and IIC. The split is based on thickness and on whether ulceration is present.
- Stage III. The melanoma has reached nearby lymph nodes or nearby skin, but not distant organs. It has subgroups, IIIA through IIID. They depend on how many lymph nodes are involved and on other features.
- Stage IV (metastatic). The melanoma has spread to distant parts of the body. Common sites are the lung, the liver, and the brain.
In short: stage depends mainly on how deep the tumor grew, whether the skin broke down over it, and how far it has spread.
What goes into a stage
Two features of the original tumor matter most:
- Thickness (Breslow depth). How many millimeters deep the melanoma has grown into the skin.
- Ulceration. Whether the skin covering the tumor has broken open. For a given thickness, ulceration usually means a more advanced stage.
Staging also looks past the tumor itself. It asks whether cancer cells are in nearby lymph nodes. That is often checked with a sentinel lymph node biopsy. It also asks whether scans show spread to distant organs.
Why it matters
Stage helps guide how much treatment is needed. Early, thin melanomas may need surgery alone. More advanced disease may need surgery plus immunotherapy or targeted therapy. Stage also gives a rough sense of outlook. But treatments for advanced melanoma have improved a lot in recent years, and every person's case is different.
When to get help sooner
- Call 911 or go to an emergency department if you have a sudden bad headache, a seizure, weakness or numbness on one side, trouble speaking, or sudden vision changes. Melanoma can spread to the brain, and these signs need care right away.
- Contact your treatment team without delay, whatever the hour, if your temperature reaches 100.4°F (38°C) or higher while you are on treatment. CDC treats fever during chemotherapy as a medical emergency, because it may be the only sign of an infection that can turn life-threatening within hours. If you cannot reach them quickly, head to an emergency department and tell staff you are in treatment.
- Call your care team the same day if a melanoma site is bleeding and will not stop, or the wound is red, hot, swollen, and draining.
- Call 911 or go to an emergency department if chest pain arrives suddenly or is severe, particularly with breathlessness.
- Call your care team within a day or two if you feel a new lump near the scar or in the nearby lymph nodes, or you have a new cough, a lingering chest ache, belly pain, or weight loss you cannot explain.
Sources
Words to know
Tap any term to see what it means.
Common questions
What does tumor thickness mean for melanoma?
Thickness, also called Breslow depth, measures how deep the melanoma has grown into the skin, in millimeters. Thicker melanomas are generally more advanced and are linked to a higher stage.
What is ulceration?
Ulceration means the skin over the melanoma has broken down. Its presence generally pushes a tumor to a higher stage within its thickness category.
Does stage III always mean the cancer has spread far?
No. Stage III means melanoma has reached nearby lymph nodes or nearby skin, but it has not spread to distant organs. Many people with stage III melanoma are treated successfully.
What does stage IV mean?
Stage IV means melanoma has spread to distant parts of the body, such as the lungs, liver, brain, bone, or distant lymph nodes. There are effective treatments for stage IV melanoma, and outcomes have improved significantly in recent years.
Why does staging matter?
Staging guides treatment decisions and gives a general sense of outlook. It is one piece of information among several your care team uses to plan your care.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Speak With Trained Specialists & Human Navigators
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Get urgent help
Immediate emergency guidance for fever (>100.4°F during chemo), severe pain, or shortness of breath.
Help Us Improve This Guide
Did this explanation answer your question and help you determine your next step?
Know someone who needs this?
Plenty of people are looking for something like this and do not know where to start. If this would help a friend or someone you love, send it on — we have written an opening line so you do not have to stare at an empty message. You can change every word of it.
Your message is written and sent in your own email or messaging app — we never see who you send it to, and nothing is added to any list.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-08-19Next planned review: 2027-08-03
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.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team 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.
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.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.
Related articles
Still have questions?
Educational answers, plain language
Free to print and share