What Is Acral Lentiginous Melanoma?

Acral lentiginous melanoma (ALM) is a rare type of cancer that affects the pigments in a person's skin, specifically on the palms of the hands, soles of the feet, and nail beds. ALM is an aggressive form of melanoma. When detected early, it can be cured by surgically removing the lesion. However, diagnosis presents challenges, especially for those who are not diagnosed early.

This article discusses the symptoms, causes, diagnosis, and treatment of ALM.

Types of Acral Lentiginous Melanoma

The two primary characteristics of ALM are:

• Location: "Acral" means "extremity" in Greek, which describes the location where this skin cancer appears (hands and feet). There's a subtype of this melanoma that is found in the nail beds, called subungual melanoma.
• Lesion coloration: "Lentiginous" refers to the freckled pigmented appearance of the spots or lesions. They can be a different, darker shade than a person's skin. However, there are also nonpigmented or amelanotic lesions, which may appear as a red or orange color.

Symptoms

There are a number of characteristic changes in the feet, hands, and nail beds associated with ALM. These include:

• A black or brown discoloration on the palms or feet soles
• A thick, elevated, or irregular growth on the hands or feet
• A dark line or streak in the length of the nail that may cause damage to the nail
• Changes in the shape or color of a mole on hands or feet
  

It's important to note that the lesions, lines, or growths can look similar to other conditions not caused by ALM. Your lesion will have to be closely examined by a healthcare provider to determine if it is ALM.

Causes

The cause of ALM is not clear.

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.

Sun exposure isn't believed to be a cause, because this type of cancer appears on parts of the body that aren't often exposed to as much UV (ultraviolet) rays from the sun.

Diagnosis

A thorough physical examination by a healthcare provider or dermatologist (skin specialist) who is familiar with this type of cancer is a key part of the diagnostic process.

For diagnosing melanoma lesions, the ABCDE system is often used to determine if any spots on the skin may be potentially cancerous.

Because of the challenges with correctly diagnosing ALM, providers may use a handheld device called a dermascope to closely examine any potential cancerous lesions. This tool allows the provider to see multiple parts of the skin that are not typically visible to the naked eye to assist with a diagnosis.

However, because of where the lesions are found on the body, misdiagnosis is common. For example, ALM lesions on the feet can be confused with plantar warts, ingrown toenails, blisters, calluses, benign (noncancerous) tumors, and ulceration.

Similarly, the characteristic sign of ALM in the nail bed is a brown or black line on the length of the nail. This type of line on the nail can be associated with trauma (such as having smashed a finger in a door) or even a fungal infection.

Being of a lower socioeconomic status, not having access to a dermatologist, not getting a full-body examination during primary care visits, and lacking information about ALM also are factors that contribute to the risk of misdiagnosis.

Treatment

Acral lentiginous melanoma is highly treatable when diagnosed and treated early. Typical treatment is surgical removal of the lesion with the aim to remove the cancer, prevent it from coming back, and maintain the appearance of the skin.

However, if ALM is more advanced and has spread elsewhere in the body, additional treatments may be necessary. These may include chemotherapy, radiation therapy, and immunotherapy.

Prognosis

Survival rates are best for those with ALM when diagnosed at an early stage. However, because diagnosis is often challenging and delayed, people with advanced ALM have a poorer prognosis.

Factors that influence survival rates include the thickness of the lesion, ulceration (a break in the skin), mitotic rate (used to help find the stage of melanoma), and how far the cancer has spread in the body. Experiencing a recurrence of the lesion is 2 to 5 times more common than other types of melanoma.

Summary

Acral lentiginous melanoma is rare type of skin cancer. It primarily affects the hands, feet, and nail beds. It is more common in Black people and Asian people. Misdiagnosis can be common, but ALM can be treated successfully with surgery if diagnosed early.

A Word From Verywell

Because ALM can be challenging to diagnose, it's important to be familiar with how your body looks so you can notice changes—like a new growth or mole—that are worth investigating. Identifying any potentially cancerous spots early with the help of a healthcare provider or dermatologist can increase the chances of early treatment and a positive prognosis. While a diagnosis of ALM can be scary, effective treatment is available when caught early.