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When you think of melanoma, you likely picture a dark, abnormally shaped mole on your arm or shoulder. However, not all melanoma lesions look the same. Acral lentiginous melanoma (ALM) is a specific type that forms on the hands, feet, and nailbeds. Since most people don’t know to look for melanoma in these spots, it can quickly become dangerous.
In this article, we’ll discuss what ALM is, its risk factors, and symptoms to look out for. We’ll also cover how doctors treat ALM and what your prognosis (outlook) is. To learn more about your ALM case, talk with your cancer specialist (oncologist). You may also get treatment from a skin specialist (dermatologist).
ALM — also known as acral melanoma — is a rare type of cutaneous melanoma (skin melanoma). It accounts for only 1 percent to 3 percent of all new melanoma cases. In the United States, doctors diagnose around 2,000 to 3,000 ALM cases every year.
ALM forms in places you likely don’t think of finding skin cancer, such as the soles of the feet or the palms of the hands. At first, it may be difficult to see because it can look like a bruise or a harmless mole.
The most common sign of ALM is a new, abnormal brown, gray, black, or tan spot on the palm or bottom of your foot. This spot may change shape or color over time. You may also see new moles that weren’t there before. Sometimes, moles you’ve had for years begin changing — be sure to get them checked out.
You should also talk to your doctor if any spots or moles start hurting, bleeding, or itching. Any new raised bumps or patches of skin on your hands or feet are worth getting looked at.
ALM can form underneath your fingernails and toenails as well. This is known as subungual melanoma. ALM typically looks like a dark streak underneath your nail that isn’t caused by a bruise. For some people — especially those with darker skin tones — nail streaks can be normal. It’s still important to see your doctor to make sure they’re not melanoma.
Melanoma develops in the melanocytes. These specialized skin cells make the pigment melanin that colors your skin. DNA mutations (changes) can form in melanocytes — especially from sun exposure. Since ALM tends to form on skin that doesn’t get much sun, researchers think other causes are to blame.
One theory is that force and stress from your weight pushing down on your feet leads to ALM. Studies show that ALM lesions tend to form on the heel and outside of the foot where the most pressure is.
Your genetics may also play a role in your ALM risk. Some people have mutations in certain genes that control how fast cells grow and divide. These mutations can lead to uncontrolled melanocyte growth and the formation of tumors.
ALM can develop in anyone, but it tends to occur in people with darker skin tones. According to research in StatPearls, ALM accounts for:
Cancer tends to affect older adults, and this is true for ALM. The average age at diagnosis is nearly 63 years. The likelihood of developing ALM rises as you get older and significantly increases after age 80. Males and females have roughly equal chances of this skin cancer, according to StatPearls — but females are more likely to be diagnosed in the early stages.
The key to treating ALM begins with early detection. Talk to your doctor if you notice any new or changing suspicious spots. They’ll take a close look at your skin for any signs of ALM and run a few tests.
Melanoma skin cancers are typically identified with the “ABCDE” criteria. This acronym outlines different characteristics of moles or lesions seen with melanoma. However, these characteristics don’t apply to ALM lesions. Experts have proposed using the acronym “CUBED” instead. It stands for:
If your doctor thinks you have ALM, they may use dermoscopy. This test uses a tool known as a dermatoscope, which has a magnifying lens and a light. Your doctor will take a close look at the lesion for signs of ALM. They may see changes in your skin cell patterns and coloring that point to skin cancer.
The only way to confirm you have ALM and avoid a misdiagnosis is with a biopsy. Your doctor will remove the mole or lesion to look at under a microscope. A pathologist (tissue specialist) will determine the stage of your ALM. Stages of melanoma range from stage 0 to stage 4, and stages are sometimes rendered with Roman numerals, for example, “stage III” instead of “stage 3.” Your cancer stage will determine which treatments you may need.
Because ALM is a rare cancer, doctors are still looking for the best way to treat it. Depending on the stage of your cancer, your treatment plan may include surgery or medications — systemic (bodywide) or topical (applied to the skin). It’s important to work closely with your oncologist and/or dermatologist to find the best plan for you.
Surgery is the most common treatment for early melanoma skin cancer — including ALM. Your doctor will likely remove the lesion. They’ll also take a small margin of healthy skin around the lesion to make sure they removed as much of the cancer as possible. Your doctor might also take nearby lymph nodes (immune system structures). This helps look for and prevent the spread of cancer to other parts of the body.
If your cancer has metastasized (spread), you’ll likely need systemic treatment. Immunotherapy helps your immune system to fight and destroy cancer cells. Studies show that immunotherapy drugs don’t work as well to treat ALM compared to other melanoma types.
Targeted therapies work by blocking proteins that melanoma cells use to grow and divide.
The BRAF mutation is common among people with ALM, and it can be treated with medications such as dabrafenib (Tafinlar) and vemurafenib (Zelboraf).
People with KIT mutations can be treated with the targeted therapy imatinib (Gleevec). It’s important to note this medication will work only if you have the specific KIT mutation.
Other topical drugs have been investigated. One example is the medication imiquimod (Aldara, Zyclara). Researchers have found imiquimod can slow ALM growth and spread, and it may even help shrink lesions. It can be used as an alternative to surgery or even before it in some cases.
People with ALM tend to have a worse prognosis than those with other types of melanoma skin cancer. This is likely because ALM is harder to detect and diagnose accurately. By the time you receive a diagnosis, the cancer may have grown to an advanced stage.
One study looked at the five-year survival rate of 392 people with ALM. This refers to the percentage of people with ALM who were alive five years after their diagnosis. The authors found the survival rates by stage were:
This means that the less advanced your ALM is, the better prognosis you have. If you notice any signs of ALM on your hands, feet, or nails, it’s especially important to get an early diagnosis. By working closely with your doctors, you can improve your outlook with this disease.
MyMelanomaTeam is the social network for people with melanoma and their loved ones. On MyMelanomaTeam, people come together to ask questions, give advice, and share their stories with others who understand life with melanoma.
Have you been diagnosed with acral lentiginous melanoma? What signs did you notice? Share your experience in the comments below, or start a conversation by posting on your Activities page.
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Leonora Valdez Rojas, M.D.
received her medical degree from the Autonomous University of Guadalajara before pursuing a fellowship in internal medicine and subsequently in medical oncology at the National Cancer Institute.
Learn more about her here.
Emily Wagner, M.S.
holds a Master of Science in biomedical sciences with a focus in pharmacology. She is passionate about immunology, cancer biology, and molecular biology.
Learn more about her here.
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