What is acral lentiginous melanoma?
In this article, we look at the symptoms of acral lentiginous melanoma (ALM), how it is diagnosed and staged, and the treatment options that are available.
Acral lentiginous melanoma affects the feet and hands, as well as the skin beneath the nails.
Image credit: Image credit: Will Blake, (2006, May 29)
Melanoma is a type of skin cancer that begins in the melanocytes. These are skin cells that give the skin its pigment.
Most people develop melanoma as a result of exposure to ultraviolet (UV) radiation from the sun. People with light skin account for most cases of melanoma since their skin is more likely to be damaged by UV radiation.
ALM is a specific type of melanoma. It affects the palms of the hands, the soles of the feet, and the skin under the nails.
Unlike other types of melanoma, it occurs with similar frequency in all people regardless of skin color. This means that people with dark skin are also vulnerable to ALM.
As people with dark skin are less prone to other forms of melanoma, ALM is the leading cause of melanoma in people with darker skin.
ALM sometimes develops from an existing mole. It can also occur seemingly out of nowhere on healthy skin.
Symptoms and appearance
ALM is more common on the soles of the feet than the palms of the hand.
Most people first notice an oddly shaped black, gray, tan, or brown mark with irregular borders.
When ALM begins in the nails, it may appear as a dark streak under the nail. Most cases of ALM on the nails occur on the big toe or thumb.
ALM is the most common type of cancer to affect the soles of the feet, but other cancers can also develop on the feet or hands. Anyone that suspects they may have cancer on the soles of their feet must seek a diagnosis from a skilled dermatologist.
Some other warning signs of ALM include:
- a new streak in a nail that is not caused by an accident or bruise
- a nail streak that has damaged the fingernail
- a changing spot in or connected to a mole on the foot or hand
- an irregularly-shaped growth on the foot or hand that is changing, growing, or has an unusual color
- an elevated, thickened patch growing on the sole of the foot or palm of the hand
Causes and risk factors
ALM may be caused by injuries or genetics in some cases, although research into risk factors is ongoing.
Image credit: Kelly Nelson, (2012, April 2)
Anyone can develop ALM. Unlike other forms of melanoma, ALM does not appear to be related to sun exposure.
In some people, it may be due to a genetic risk factor. People whose family members have developed melanoma, including ALM, may be more prone to the disorder.
Research into the specific causes and risk factors for ALM is ongoing. Some research suggests that an ALM lesion may follow an injury to the hand or foot.
However, most people with ALM do not have an injury, and most people who injure their hands or feet never develop ALM.
Tests and diagnosis
Diagnosis with ALM begins with an examination of the affected area. ALM and other forms of cancer have a particular appearance that will help a doctor decide which tests are appropriate.
A doctor may use an instrument called a dermatoscope to get a closer look at the growth.
A sample allows a pathologist to look at the tumor under a microscope to see if it is cancer, how invasive the cancer is, and how the cells of the cancer are behaving.
Assigning a stage to an ALM lesion helps doctors predict survival and determine a treatment plan. Like other forms of melanoma, ALM staging looks at three factors:
- Tumor: Numbers range from 0–4 and denote the size of the tumor, and whether it shows ulcerations. Lower numbers indicate a smaller tumor.
- Nodes: This indicates whether lymph nodes have been affected, and the scale ranges from 0–3.
- Metastasis: Metastasis is the spread of cancer from one area of the body to another. When cancer metastasizes, it is more likely to be fatal. Metastasis scores range from 0–1. A score of 1 indicates some metastasis, with letters a, b, and c indicating progressively more spreading.
Doctors may also assign the tumor a Clark level. This provides information about how much the tumor has invaded the body.
Clark levels range from 1–5, with higher numbers pointing to more invasive cancers.
Treatment usually begins with removing the lesion and occasionally some skin surrounding the lesion. If any lymph nodes are affected by cancer, they might also need to be removed.
In some people, this cures the cancer. But if the cancer has progressed or is very aggressive, other treatments may be necessary.
If removing the tumor does not completely get rid of the cancer, doctors may recommend medication to prevent the cancer from spreading. The United States Food and Drug Administration (FDA) have approved the drug aldesleukin (Proleukin) to treat ALM.
Because ALM is relatively rare, it is also poorly understood. A number of clinical trials seek to understand the disease better and find more effective treatments. Some people may be able to take part in clinical trials when other treatments fail, or if they are not healthy enough for other treatments.
Since the causes of ALM are not known, there is no sure way to prevent it. However, early diagnosis may support successful treatment and recovery.
Wearing sunscreen, avoiding bright sunlight, and minimizing sunburns can prevent most forms of melanoma. However, ALM appears unrelated to sun exposure.
As researchers do not yet know what causes ALM, they also do not know how to prevent it.
The best opportunity for a favorable outcome is a prompt diagnosis. People can seek annual skin exams to test for skin cancer, and should promptly see a doctor if an unexplained lesion appears on a hand, foot, or nail.
Prognosis and outlook
Death rates from ALM are higher than those of other forms of melanoma. This may be because ALM goes unnoticed longer, allowing it to progress and become more aggressive before treatment begins.
Early diagnosis and prompt treatment have a major impact on whether a person will survive. However, a large number of people who have ALM are initially misdiagnosed with something else.
Less advanced cancers and thinner tumors have better survival rates. Raised tumors tend to be more aggressive.
Men are more likely than women to have thick, large tumors at diagnosis. A person's race is also a factor, with non-Hispanic whites having lower rates of similar tumors at the time of diagnosis.
Researchers do not know why survival and cancer aggression seems to vary across different groups. It could be due to differences in medical care or because some groups are more likely to notice and seek treatment for signs of skin cancer.
Because of these differences, survival rates vary by group:
- 5-year survival rates for non-Hispanic white people are 82.6 percent, with 69.4 percent surviving to 10 years.
- 5-year survival rates for African-American people are 77.2 percent, with 71.5 percent surviving to 10 years.
- 5-year survival rates for Hispanic people are 72.8 percent, with 57.3 percent surviving to 10 years.
- 5-year survival rates for Asian people and Pacific Islanders are 70.2 percent, with 54.1 percent surviving to 10 years.
Though ALM is rare, it can be deadly. Monitoring the skin for changes can be life-saving.
People who worry they may have ALM should seek treatment with a skilled dermatologist who understands ALM.
With aggressive treatment, most people can survive this disease.