Bruise or Melanoma? How to Tell the Difference

A bruise (contusion) is blood that has leaked from small vessels into the surrounding tissue after an impact. Fresh bruises look red or purple, then evolve through a recognisable colour sequence as the blood breaks down: purple-blue, then green, then yellow-brown, before fading away entirely.

That colour progression is the signature of a bruise. Crucially, a bruise resolves on a timeline — most fade noticeably within 1-2 weeks and are gone by 2-3 weeks. A bruise is also usually tender at first and linked to a remembered injury.

The mimics are acral lentiginous melanoma (on palms, soles, fingers, and toes) and subungual melanoma (under a nail). Both can appear as a dark brown, black, or blue-black patch or streak that looks, at a glance, like a bruise from a stubbed toe or a pinched finger.

The difference is that melanoma does not move through the bruise colour cycle and does not fade. It stays, and it may slowly grow, darken, or develop irregular borders and multiple shades. A 'bruise' that is still there after a month — and is not progressing through purple-green-yellow toward disappearing — is a reason to be seen.

Bruise: passes through purple, green, and yellow-brown as it heals, then disappears. The colour change reflects haemoglobin breaking down.

Melanoma: stays brown, black, or blue-black. It does not turn green or yellow, because the colour comes from melanin in cells, not from blood being reabsorbed. The absence of the bruise colour sequence is one of the clearest tells.

Bruise: fades within 2-3 weeks. You can watch it shrink and lighten week by week.

Melanoma: persists or grows over weeks to months. The most practical test is to photograph the spot with a date and recheck in two to three weeks. A real bruise will be clearly fading or gone. A 'bruise' that is unchanged or larger at that point needs a dermatologist.

Subungual bruise: usually starts after a clear injury (dropped object, stubbed toe), is tender at onset, and grows out with the nail. Over weeks you can see a gap of normal nail appearing at the base while the dark mark migrates toward the tip.

Subungual melanoma: typically a brown-black band or patch that does not grow out, may widen over time, and often shows the Hutchinson sign — pigment spreading from under the nail onto the surrounding cuticle or skin fold. That pigment extending beyond the nail is a strong melanoma signal and needs urgent assessment.

Acral bruise: follows the colour cycle and fades, linked to a known impact or friction.

Acral melanoma: a persistent dark patch on a palm, sole, or between digits. On magnified examination dermatologists look for a parallel ridge pattern — pigment following the ridges of the skin in straight parallel lines. Acral melanoma is the subtype most often missed because it is mistaken for a bruise, blister, wart, or fungal mark, so any non-fading dark patch in these areas deserves attention regardless of skin tone.

Bruise: tied to a remembered or plausible injury and tender at first. Easy bruising elsewhere on the body points to a benign cause (blood thinners, age, minor knocks).

Melanoma: often has no clear injury, or a vague one invented to explain a spot that does not fit the bruise pattern. A solitary, persistent dark mark with no real injury behind it — especially on a hand, foot, or under a nail — is the pattern to take seriously.

Book a dermatologist if a 'bruise' is: still present and not fading at 3-4 weeks; on a palm, sole, finger, toe, or under a nail with no clear injury; a band under a nail that is widening or not growing out; showing pigment spreading onto the skin around a nail (Hutchinson sign); or developing irregular borders or multiple colours.

Book urgently (within a week) for pigment extending beyond the nail, a rapidly changing dark patch, or any concerning lesion in someone with a melanoma history. Subungual and acral melanoma are very treatable when caught early; the reason to act is that they are most often missed by being dismissed as bruises.