Acral Melanoma: The Skin Cancer on Palms, Soles & Under Nails
Acral lentiginous melanoma (ALM) accounts for only 2-3% of all melanomas in light-skinned populations but represents 35-60% of melanomas in Black, Hispanic, and Asian patients. It occurs on the palms, soles, and under nails — areas with minimal sun exposure, which is why it is often missed by traditional screening focused on sun-damaged skin.
What acral melanoma looks like
On palms and soles: an irregularly pigmented patch or lesion — brown, black, or multi-colored. It may look like a bruise that does not go away. Early ALM can be as small as a few millimeters and easy to overlook.
Under nails (subungual melanoma): a dark longitudinal streak running from the cuticle to the tip. Not every dark streak is melanoma — pigmented bands are common in darker skin. Warning signs: the streak is wider than 3mm, has multiple colors, is widening, or the pigment extends beyond the nail onto the surrounding skin (Hutchinson sign).
Who is at risk
ALM has a different risk profile than other melanomas. UV exposure is not a major factor. It occurs equally across all levels of sun exposure. Risk factors include: age over 60, history of trauma to the area (though trauma does not cause melanoma — it may lead to earlier detection), and possibly genetic factors not yet well understood.
Ethnicity matters not because of biological susceptibility but because of diagnostic delay: ALM is the most common melanoma subtype in Black, Hispanic, East Asian, and South Asian populations, yet screening protocols rarely focus on acral sites.
Why it is often diagnosed late
Several factors contribute to delayed diagnosis. Patients may not check their palms, soles, or nails during self-exams. Doctors may not examine these areas during routine skin checks. A dark spot on the sole may be attributed to a callus, bruise, or fungal infection. A nail streak may be dismissed as a bruise or normal pigmentation.
The result: ALM has a worse prognosis than other melanoma types — not because it is biologically more aggressive, but because it is found at a later stage.
How to check for acral melanoma
Monthly self-exam of acral sites takes 2 minutes: Check both palms, including between fingers and in creases. Use a mirror (or phone camera) to check the soles of both feet, including between toes. Examine all fingernails and toenails for dark streaks. Look inside your mouth (gums, palate, inner cheeks).
What to look for: new dark spots, expanding patches, dark streaks in nails, non-healing sores, lesions that bleed easily.
Acral melanoma vs bruise vs fungus
A subungual bruise (from trauma) grows out with the nail over weeks to months. You can often trace it to an injury. A fungal nail infection causes yellowing, thickening, and crumbling — not a dark streak.
Acral melanoma: persists regardless of nail growth, may widen over time, and does not resolve. If you have a dark spot on a palm or sole that has lasted more than a month, or a nail streak with no trauma history, see a dermatologist.
Dermoscopy can often distinguish melanoma from benign pigmentation, but biopsy is the definitive test.
Notice a dark spot on your palm, sole, or nail? See a dermatologist — this is not a mole for self-screening tools.
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