From suspicious spot to answer
Melanoma is diagnosed by a pathologist looking at tissue under a microscope. Everything before that, the exam, the dermatoscope, even an AI tool, only decides whether tissue gets taken.
Last reviewed August 21, 2026. Every factual claim on this page is sourced below. Guidance and regulations change, and a page can fall behind its sources: check the linked source before acting on anything here.
1. The clinical examination
The dermatologist takes a history and examines the area, noting “the size, shape, color, and texture of the area(s) in question, and whether it is bleeding, oozing, or crusting.” They will also feel the nearby lymph nodes, because “when melanoma spreads, it often goes to nearby lymph nodes first, making them larger.”
2. Dermoscopy
A dermatoscope, “a special magnifying lens and light source held near the skin,” reveals pigment patterns below the surface. Digital versions can store images to track change across visits, and some systems apply computer analysis to help estimate the likelihood of melanoma. This is a triage step, not a diagnosis.
3. The biopsy
If the lesion is suspicious, tissue is removed. Four techniques are in common use.
| Type | What it removes | Typically used when |
|---|---|---|
| Excisional | “The entire abnormal area, along with a small margin of normal skin around it” | The preferred method for suspected melanoma. It gives the pathologist the whole lesion, including its full depth |
| Punch | A deeper cylinder of skin, taken with “a tool that looks like a tiny, round cookie cutter”; usually closed with stitches | When a deeper sample is needed but full removal is not practical |
| Shave | The top layers of skin, with a surgical blade; a deep shave (saucerization) takes more | Lower-risk lesions; the deep version for higher-risk ones |
| Incisional | Part of the lesion only | When the lesion is too large to remove whole at this stage |
The reason excisional is preferred is depth. How far a melanoma has grown into the skin drives the entire prognosis and treatment plan, and a technique that removes only the top of a lesion can leave that measurement unknowable. If a shave biopsy is proposed for something a clinician considers likely melanoma, it is entirely reasonable to ask why.
4. The pathology report
A pathologist examines the sample for melanoma cells and measures “important features such as the tumor thickness and mitotic rate (the proportion of cells that are actively dividing).” Thickness, the Breslow depth measured in millimeters, is the number that matters most for what happens next. Molecular testing may look for mutations such as BRAF, which determine whether particular targeted therapies are options.
5. Sentinel lymph node biopsy
For higher-risk melanomas, a sentinel lymph node biopsy checks whether cancer has begun to spread. A radioactive tracer identifies the first nodes the lesion drains into; those nodes are removed and examined. If no melanoma cells are found, “no more lymph node surgery is needed.”
What stage means for outcome
Five-year relative survival, from the National Cancer Institute’s SEER program (SEER 21 excluding Illinois, 2016-2022). Stage shares are rounded to the nearest percent and do not total exactly 100%:
| Stage at diagnosis | Share of cases | Five-year relative survival |
|---|---|---|
| Localized, confined to the skin | 77% | 100.0% |
| Regional, spread to nearby nodes | 10% | 76.0% |
| Distant, spread to distant sites | 5% | 34.0% |
| Unstaged | 9% | 95.4% |
| All stages combined | 94.7% |
Relative survival compares people with the diagnosis to people without it, so it isolates the effect of the cancer. These are population figures from people diagnosed years ago; they describe a group, not an individual, and they do not yet reflect the full effect of treatments introduced recently. The reason to look at them is the shape rather than the precision. The drop from localized to distant is the argument for every other page on this site.
Next
What a screening appointment involves →
Where AI actually fits into this →
Sources
- American Cancer Society, Tests for Melanoma Skin Cancer.
- National Cancer Institute SEER, Cancer Stat Facts: Melanoma of the Skin, SEER 21 excluding Illinois, 2016-2022.