You’re staring at your thumb. There is a dark line there, maybe a smudge of brown or a streak that looks like you slammed your finger in a door three weeks ago, but you don't remember any door. You’ve been scrolling through photos of melanoma under fingernail for twenty minutes now. Honestly, it’s terrifying. The internet has a way of making every hangnail look like a death sentence, but with subungual melanoma—that's the medical term for it—the stakes are legitimately high. It is rare, accounting for maybe 0.7% to 3.5% of all melanomas worldwide, yet it’s often caught way too late because people think it’s just a bruise.
It isn't just a "dark spot."
When you look at actual clinical images, you notice patterns. Or rather, a lack of them. A bruise (subungual hematoma) usually grows out with the nail. If you take a photo today and another in a month, a bruise will have moved toward the tip. Melanoma? It stays put at the base because the factory—the nail matrix—is where the cancer lives. It keeps pumping out pigmented cells as the nail plate slides over it. This creates a longitudinal streak.
What the Photos Don't Always Tell You
Most people expect a jet-black line. Reality is messier. Sometimes it’s a faint, watery brown. Other times, it’s a "melanotic" lesion, meaning there’s no pigment at all. Yeah, you can have melanoma that’s flesh-colored. That’s why looking at photos of melanoma under fingernail can be a double-edged sword; you might see a horror show of a decaying nail and think, "Mine doesn't look like that, I'm fine," when in reality, yours is just in an earlier, more treatable stage.
Dr. Richard Scher, a renowned nail specialist, has often pointed out that the "Hutchinson’s sign" is the big red flag. Look at the skin around the nail. If the pigment spills over onto the cuticle or the nail fold, that is a massive warning sign. Healthy nails don't leak color onto the skin.
The ABCDEF Rule for Your Nails
Dermatologists don't just wing it. They use a specific mnemonic.
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A is for Age. Peak incidence is usually between 50 and 70 years old, and it's notably more common in individuals with darker skin tones (African American, Asian, and Hispanic populations), where it can account for up to 15-20% of melanoma cases.
B is for Band. Look at the width. Is it more than 3 millimeters? Is the border blurry or sharp? Blurry is bad.
C is for Change. This is the clincher. If that band was thin and now it's wide, or if it was light brown and now it's turning black, you need a biopsy yesterday.
D is for Digit. The thumb is the most common victim. Followed by the big toe. Why? Nobody is 100% sure, but some theories suggest it’s related to trauma, though the link between hitting your thumb and getting cancer isn't definitively proven like UV rays are for skin melanoma.
E is for Extension. That’s the Hutchinson sign we talked about. Pigment on the skin.
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F is for Family history. ### Comparing Real Cases vs. Common Mimics
Let's get real about what else it could be. Because 9 times out of 10, it’s not cancer.
Fungal infections can turn a nail black or brown. But usually, the nail gets thick, crumbly, and gross. Melanoma usually leaves the nail surface smooth, at least initially. Then there's ethnic racial pigmentation. Many people of color have multiple brown lines on multiple fingers. This is totally normal. It’s called melanonychia striata. The key difference? Those lines are usually stable. They don't change. They've been there for years.
If you see a splinter hemorrhage, it looks like a tiny, tiny piece of wood stuck under the nail. It's actually a tiny burst blood vessel. These are usually vertical, very thin, and—most importantly—they move as the nail grows.
The Biopsy Scare
If you go to a dermatologist and they don't like what they see in your photos of melanoma under fingernail, they will suggest a biopsy. This is the part everyone hates. They have to take a piece of the nail matrix. It sounds medieval. It can leave a permanent split in your nail. But compare a split nail to the alternative. If subungual melanoma metastasizes, the survival rates drop significantly. Early detection, where the "In Situ" stage is caught, has a nearly 100% 5-year survival rate. If it's caught late? It's a different, much harder conversation.
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Dr. Shari Lipner at Weill Cornell Medicine is a leading expert here. She often emphasizes that we shouldn't wait for the nail to start lifting off the finger (onycholysis) or bleeding. By the time the nail is falling apart, the cancer has likely invaded deep into the tissue.
Why You Can't Just Trust a Google Search
Algorithms are great for finding recipes. They are "sorta" okay at diagnosing skin stuff, but they fail on nails constantly. Reflections on the nail plate, poor lighting in your bathroom, and the sheer variety of how human bodies react to trauma make DIY diagnosis a gamble.
I’ve seen people post in forums convinced they have melanoma because of a purple spot. It turned out to be a blood blister from gardening. I've also seen people ignore a "pencil mark" on their ring finger for three years until it became a nodule.
Actionable Steps for Your Next 24 Hours
Stop looking at low-resolution photos of melanoma under fingernail on Reddit. It’s just going to spike your cortisol.
- The Sharpie Test. Take a fine-tip permanent marker. Draw a tiny dot on your nail plate exactly where the top edge of the pigment is.
- Wait and Watch. Check it in three weeks. Has the pigment moved past the dot? If the pigment stayed behind the dot (near the cuticle) and the dot moved toward the tip, the pigment is likely stationary in the matrix. That is a prompt for an immediate doctor visit.
- Check Your Cuticles. Grab a magnifying glass. Is the skin around the nail perfectly clear? Any "staining" on the skin is an emergency.
- Remove All Polish. You can't monitor what you can't see. If you have a suspicious streak, keep that nail bare so you can track changes.
- Book a Specialist. Don't just go to a GP. Go to a board-certified dermatologist. If you can find one who specializes in "nail disorders," even better.
If the doctor says "it's probably nothing, let's watch it," ask them for a specific timeline. "How long should we watch it? If it hasn't moved in two months, can we biopsy then?" Be your own advocate. Nails grow slow—about 3 millimeters a month—so patience is part of the process, but vigilance is the part that saves your life.
The reality is that subungual melanoma is a "great masquerader." It hides in plain sight. It pretends to be a bruise. It pretends to be a fungus. But once you know the signs—the widening band, the dark skin around the nail, the lack of movement—you’re no longer guessing. You're taking control.---