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At first, it may look like nothing more than a dark line on your nail. Maybe you assume it’s a bruise. Maybe you think you bumped your finger and forgot about it. But sometimes, that subtle stripe can signal something far more serious: subungual melanoma, a rare yet aggressive form of skin cancer that develops under the nail.
Although it represents a small percentage of melanoma cases worldwide, subungual melanoma is considered particularly dangerous — not because it spreads faster than all other types, but because it is frequently diagnosed late. And in cancer, timing can make all the difference.
Understanding what to look for could quite literally protect your finger — and your life.
🔍 What Does Subungual Melanoma Look Like?
The most common presentation is a longitudinal pigmented band running from the base of the nail (cuticle area) to the free edge.
Here are the key visual features:
• A brown, dark brown, or black stripe
• A band that runs vertically (from cuticle to tip)
• Progressive widening of the stripe over time
• Irregular borders or uneven coloration
• Pigment spreading onto surrounding skin
One particularly important clinical sign is called the Hutchinson sign — when the pigment extends beyond the nail plate and onto the cuticle or surrounding skin folds. This is considered a red flag and requires urgent evaluation.