Causes of Acral Lentiginous Melanoma

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Acral lentiginous melanoma (ALM) is a rare aggressive type of skin cancer that affects the pigments in a person's skin. It most commonly develops on the palms of the hands, soles of the feet, and nail beds.

The underlying cause of ALM is poorly understood, but one thing is clear: Unlike other forms of skin cancer, it is not related to sun exposure. This means that those with darker-skinned complexions, who are generally less likely to develop most types of skin cancer, are at equal risk of getting ALM as those with lighter skin pigmentation. 

This article will review the potential causes of ALM and what to know about your risk.

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Common Causes

Acral lentiginous melanoma (ALM) is a subtype of cutaneous melanoma. This means that this skin cancer arises when melanocytes—the cells responsible for making the pigment that determines the color of the skin (melanin)—grow out of control and form tumors.

The exact cause of ALM is unknown. Unlike most skin cancers, ALM is not associated with exposure to sunlight.

The pigment melanin offers some protection from ultraviolet (UV) radiation, so people with darker complexions usually have a slightly lower risk of skin cancer than people with lighter complexions. But since ALM is not associated with UV exposure, those with darker-skinned complexions are just as likely to get this type of cancer as those with lighter-colored skin.

ALM and People With Dark Skin

ALM is a rare form of skin cancer, comprising 2%–3% of all melanoma cases. However, it is the most common type of malignant melanoma in people who traditionally have dark skin, particularly Black Americans, and people of Asian, and Middle Eastern origin.

While sun exposure and other lifestyle factors, such as smoking, have not been linked to ALM, researchers have identified some other factors that may increase your risk of ALM. These include:

  • Prior traumatic injury (or microtraumas, injury caused by repetitive stress to tissues) to the hand or foot
  • Exposure to certain agricultural chemicals
  • Systemic inflammation

However, there is not enough evidence to make a causal link between ALM and any of the aforementioned factors.

Genetics

As with most skin cancers, ALM is thought to be caused by gene mutations (changes) to melanocytes, which prompt these cells to grow out of control.

Certain genes (called tumor suppressor genes) are tasked with fixing mistakes in DNA, which helps keep the growth of cells under control. However, genetic mutations can cause tumor suppressor genes to be turned off. This can lead to cells growing out of control and can cause cancer like ALM.

ALM has been shown to be caused by mutations in the KIT, BRAF, NRAS, and NF1 genes. Specifically, mutations to the KIT gene are seen in over one-third of acral melanoma cases.

Additionally, one study identified mutations in the cyclin D1 gene in 45% of ALM cases, but more research is needed to uncover the role of these genes in the cause and propagation of this deadly disease.

Gene mutations can be acquired or inherited. In most cases, mutations of genes that are associated with ALM happen during a person’s lifetime and aren’t inherited from their parents.

But there may be a genetic component associated with the development of this type of melanoma. One study found people who had ALM were more likely to have had another type of cancer or a family history of a cancer other than melanoma.

Lifestyle Risk Factors

While lifestyle factors such as smoking, diet, and exercise have not been linked to increased risk for ALM, it is important to note that maintaining a healthy weight, not smoking, exercising, and eating a healthy diet always limit your cancer risk.

Summary

The specific cause of ALM remains a mystery. Certain genetic mutations, inflammation, and trauma to the hands and feet may put you at higher risk of getting ALM, but more research is needed to find the causal factors that put you at higher risk of developing this potentially fatal condition.

A Word From Verywell

There is a misconception that melanoma only occurs in sun-exposed areas of the skin and that people with darker skin are not at risk for melanoma. As a result, some people may overlook changes to their skin, which can delay the diagnosis of ALM. This can lead to ALM being discovered in later stages, when it is less treatable.  

Knowing the signs and symptoms of ALM is crucial to early diagnosis and treatment. If you notice an oddly shaped black, gray, tan, or brown mark with irregular borders on your body, especially on the palms of your hands and soles of your feet, contact a healthcare professional to get it checked.

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