Acral lentiginous melanoma (ALM) is a rare subtype of melanoma that often appears on the palms, soles, or under the nails. Unlike many other melanomas, ALM can develop on areas with little or no sun exposure and may be overlooked in early stages.
Understanding what acral lentiginous melanoma looks like helps you notice changes sooner and seek medical evaluation. Early detection and treatment significantly improve outcomes for this type of melanoma.
| Feature | Appearance on Skin | Common Locations | When to See a Doctor |
|---|---|---|---|
| Color | Dark brown to black, but can be tan, gray, or even pink or red | Palm, sole, nail bed | Color is uneven or rapidly changing |
| Shape | Asymmetric with irregular borders | Feet most common, then hands and nail areas | Border is scalloped, notched, or blurred |
| Size | Often larger than 6 mm, though it can start smaller | Palms and soles where moles are less common | Size increases over weeks or months |
| Texture | May be flat or slightly raised, surface can be smooth, scaly, or crusted | Under nails as a dark streak that widens | New spot, change in an existing mark, or non-healing sore |
Early Visual Signs of Acral Lentiginous Melanoma
In the earliest stage, ALM often appears as a flat patch with subtle color changes. These patches may be easily mistaken for a bruise, fungal infection, or trauma-related mark. Because there is no raised mole shape initially, people may delay seeking care.
The most helpful approach is to monitor any new or changing pigmented spot on the palm, sole, or nail area. Use the ABCDE guide adapted for acral sites: Asymmetry, Border irregularity, Color variation, Diameter, and Evolution over time.
How ALM Develops Over Time
As acral lentiginous melanoma progresses, the patch becomes more noticeably darker and the area may thicken. Pigmentation can spread outward from the original site, and the surface may become scaly or ulcerate. In some cases, the lesion may develop a wart-like or crusted appearance before medical evaluation occurs.
In advanced stages, the melanoma can invade deeper layers of the skin, leading to swelling, bleeding, or pain. Recognizing these evolving features is critical because early-stage disease is highly treatable.
Dermoscopy and Diagnostic Clues
Dermatologists use dermoscopy to examine ALM lesions more closely, revealing patterns not visible to the naked eye. Common dermoscopic features include parallel ridge patterns, diffuse or uneven pigment networks, and focal hypopigmentation. These patterns help differentiate ALM from benign acral nevi or other conditions.
When there is any doubt, a biopsy provides a definitive diagnosis. Early referral to a specialist when suspicious changes are noted can make a substantial difference in treatment options and prognosis.
Prevention and Skin Self-Monitoring
While there is no guaranteed way to prevent ALM, regular skin checks and sun protection support overall skin health. Examining your palms, soles, and nail beds monthly helps you become familiar with your usual markings and spot new or changing lesions quickly.
- Check nail beds for new brown or black streaks that widen over time
- Look at palms and soles for new spots or changes in existing freckles
- Document size, color, and shape with photos to track subtle changes
- Schedule a professional skin exam annually or sooner if you notice suspicious changes
- Protect hands and feet with sunscreen and protective footwear when outdoors
Recognizing Patterns for Earlier Detection
Familiarity with the typical appearance of acral lentiginous melanoma empowers you to seek timely care. Regular self-skin checks, attention to high-risk sites, and professional evaluations when something changes form the foundation of early detection and better outcomes.
FAQ
Reader questions
Can acral lentiginous melanoma appear on areas other than palms, soles, and nails?
Yes, although it is most common on these sites, ALM can occasionally arise on mucosal surfaces or other non-sun-exposed areas. Any new or changing dark patch in unusual locations should be evaluated by a dermatologist.
How can I tell the difference between a benign mole and ALM on my foot?
Benign foot moles are often smaller, symmetric, and uniformly colored, while ALM tends to show color variation, irregular borders, and gradual enlargement. Because early ALM can resemble a benign freckle, professional evaluation is essential for any suspicious changes.
Is a dark streak under my nail always a sign of acral lentiginous melanoma?
Not always, since trauma or fungal infections can cause dark streaks. However, a streak that widens, darkens, or involves the nail fold should be examined promptly. Early diagnosis of nail matrix melanoma improves treatment outcomes.
What should I do if I notice a new spot on my palm that looks like a bruise?
Monitor the spot for weeks; if it does not fade like a typical bruise, grows, or changes color, see a healthcare provider. Prompt evaluation can distinguish a harmless bruise from conditions like acral lentiginous melanoma.