You’re staring at your thumb. There’s a line. It’s thin, brown, and looks almost like you drew it on with a fine-tip Sharpie, but it won't wash off. Your mind immediately goes to the worst-case scenario because you saw a TikTok or a Reddit thread about subungual melanoma. Honestly, it’s scary. Most people assume a splinter or a bruise from slamming their finger in a door, but when that "bruise" doesn't grow out with the nail, the panic sets in. Searching for melanoma in the nail pictures usually brings up a gallery of horrors—thick, black bands and crumbling nail beds—but the reality of early detection is often much more subtle.
Subungual melanoma is rare. It accounts for about 0.7% to 3.5% of all melanomas worldwide. While that sounds small, for those in the Black, Asian, and Hispanic communities, this specific type of skin cancer makes up a much larger percentage of total melanoma cases. It doesn't care if you've never had a sunburn. It doesn't care if you wear SPF 50 every day. This isn't about UV rays; it's about genetics and trauma to the nail matrix.
What you’re actually seeing in those photos
When you look at melanoma in the nail pictures online, you’re usually seeing something called melanonychia. That’s the medical term for pigment in the nail. But here’s the thing: most melanonychia is totally benign. It could be a "nail mole" (a melanocytic nevus) or just ethnic pigmentation.
If you see a picture of a dark band that is wider at the bottom (near the cuticle) than at the top, that’s a massive red flag. Why? Because it suggests the pigment-producing cells are becoming more active or growing. A stable, narrow line that stays the same width for years is generally less concerning to a dermatologist than a line that looks like it’s bleeding into the surrounding skin.
The Hutchinson Sign
This is the big one. If you look at a photo and the brown or black color isn't just on the nail plate but is actually creeping onto the cuticle or the proximal nail fold, doctors call that a Hutchinson sign. It’s named after Sir Jonathan Hutchinson, and it’s a classic clinical marker for subungual melanoma. In many melanoma in the nail pictures, this is the "gotcha" moment. If the skin around your nail is changing color, stop reading and book an appointment.
The ABCDEF Rule (It’s different for nails)
We all know the ABCDEs for moles on the skin—Asymmetry, Border, Color, Diameter, Evolving. But for nails, doctors use a modified version developed by Dr. Levit and colleagues.
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A stands for Age. This typically hits people in the 5th to 7th decades of life. It’s rare in kids.
B is for Band. Look for a brown-black band wider than 3 millimeters with blurred borders. If the edges of the line are fuzzy like a watercolor painting rather than a crisp pen stroke, take note.
C is Change. This is the most critical factor. Did the nail suddenly get darker? Did the shape of the stripe warp?
D is Digit. The thumb is the most common site, followed by the big toe. For some reason, these "high-use" digits are the primary targets for subungual melanoma. If you have lines on ten different fingers, it’s probably just systemic pigmentation or a side effect of medication. If it's just one thumb? That’s when the suspicion rises.
E is for Extension. That’s the Hutchinson sign we talked about earlier—the pigment moving to the cuticle.
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F is Family History. If your family has a history of melanoma, your threshold for getting things checked should be zero.
It’s not always cancer (Common Lookalikes)
Don't spiral just yet. Most of what people fear is melanoma turns out to be a subungual hematoma. Basically, a bruise under the nail. You hit your finger, blood pools, and it turns dark.
How do you tell the difference?
A bruise will grow out. As your nail grows, the dark spot should move toward the tip. If you take a photo today and another one in a month, and the spot is in the exact same place relative to the cuticle, it’s not a bruise. It’s something growing in the nail matrix.
Fungal infections can also mimic melanoma in the nail pictures. Certain fungi produce melanin, turning the nail black or green. Usually, fungal infections come with debris under the nail or a thickening of the nail plate that feels "chalky." Melanoma usually (though not always) keeps the nail plate smooth in its early stages.
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Why a biopsy is the only way to be sure
You cannot diagnose this through a screen. Period. Even the best dermatologist using a dermatoscope—a high-powered magnifying tool with polarized light—sometimes can't say for certain.
The gold standard is a punch biopsy of the nail matrix. This sounds unpleasant because, well, it is. They have to numbing your finger, sometimes remove a portion of the nail plate, and take a tiny piece of the tissue where the nail is born. If they catch it early (Melanoma in situ), the cure rate is incredibly high. If you wait until the nail starts cracking or bleeding—which you might see in advanced melanoma in the nail pictures—the prognosis gets much more complicated.
Real-world nuance: The "Amelanotic" trap
Here is something most "health" blogs won't tell you: sometimes melanoma in the nail has no color at all. These are called amelanotic melanomas. Instead of a dark line, you might see a persistent "sore" under the nail or a spot where the nail keeps splitting in the same place. It might look like a "proud flesh" or a pyogenic granuloma. If you’ve been treated for a "nail fungus" or a "wart" for six months and it isn't getting better, it’s time for a second opinion.
Practical steps for anyone worried about a nail line
First, remove all nail polish. You’d be surprised how many people go to the derm for a skin check and leave their toes painted. Doctors can’t see through OPI "Big Apple Red."
- Document the line. Take a clear photo in natural light next to a ruler. Do this today.
- Check the other nails. If you have similar faint lines on multiple fingers, it is statistically much more likely to be a benign condition like longitudinal melanonychia, often seen in darker skin tones due to active melanocytes.
- Wait and watch—but only for a month. If it’s a bruise, you’ll see a gap of clear nail appearing at the base within 4 to 6 weeks.
- Find a specialist. If you are going to see a doctor, try to find a dermatologist who specializes in "nail disorders." Not all derms spend a lot of time on nails; many are focused on cosmetic Botox or general acne. You want someone who knows how to use a dermatoscope on a nail plate.
Early detection is the difference between a simple surgical excision and needing a partial amputation or systemic immunotherapy. If you see a dark band that is new, changing, or affecting the cuticle, ignore the "it’s probably nothing" voice in your head. Get it looked at.
Next Steps for Monitoring:
- Perform a monthly "Nail Check" alongside your skin check, looking specifically for any pigment that touches the cuticle.
- If a biopsy is recommended, ask if it will be a "shave" or "punch" biopsy to understand the potential for permanent nail scarring.
- Review your current medications; drugs like chemotherapy agents or even some antimalarials can cause dark nail lines that mimic melanoma.