Archive · 2 Sep 2026
Nail Changes That May Signal Rare Nail-Unit Melanoma
Doctors may look at your nails when checking your health.
Dark lines on nails often have harmless causes.
But a new dark line on just one nail can be concerning.
It is more important to have it checked if the line gets wider.
Uneven colors or irregular edges are also warning signs.
The line may also spread onto the skin around the nail.
A rare cancer called nail-unit melanoma can cause these changes.
It may not hurt, so nail changes that last or worsen should be examined by a doctor.
Dark nail streaks, called longitudinal melanonychia, can have harmless causes.
A new streak affecting only one nail should be medically evaluated.
Warning changes include widening, irregular colors, or uneven borders.
A streak that extends onto the surrounding skin also needs attention.
Nail-unit melanoma is rare and may develop without pain, so persistent or worsening changes should be checked.
- Who
- Doctors and people with new or changing dark nail streaks.
- What
- Certain nail changes may require evaluation for possible nail-unit melanoma.
- When
- When a streak is new, persistent, or becomes wider or otherwise changes.
- Where
- On a single nail, potentially extending onto the surrounding skin.
- Why
- These features can sometimes occur with nail-unit melanoma, a rare form of skin cancer.
- Nail streak name
- Longitudinal melanonychia
- Potentially concerning pattern
- A new streak affecting a single nail
- Warning change
- The streak becomes wider
- Additional warning signs
- Irregular colors or borders
- Possible spread
- Extension onto the surrounding skin
- Important symptom detail
- Nail-unit melanoma can develop without pain
- Recommended action
- Have persistent or progressing changes medically evaluated