Acral Lentiginous Melanoma: Causes, Prevention and Treatment

Acral Lentiginous Melanoma (ALM), or acral melanoma, is a rare form of skin cancer. The aggressive melanoma disproportionately affects Black people and those of Asian descent. Learn more about acral lentiginous melanoma, what causes it, and how to prevent or treat it.

What Is Acral Lentiginous Melanoma? 

ALM is a rare type of melanoma, most dangerous form of skin cancer. Symptoms of ALM include asymmetrically shaped dark spots with clearly defined borders. ALM may be difficult to recognize as skin cancer because it might look similar to a bruise or stain.

Sometimes, Acral Lentiginous Melanoma can mimic plantar warts in appearance. It often occurs on the soles of the feet and lesions may cause pain when walking. They can appear flat, or as raised, thickened patches.

ALM also manifests as nail streaks on the toenails and fingernails. Warning signs include dark stripes under the nails that were not caused by a bruise or injury. Cancerous streaks may be mistaken for fungal infections.

How Does ALM Differ from Other Types of Melanomas?

Acral lentiginous melanoma differs from other types of melanomas in that it develops on parts of the body that aren’t typically exposed to the sun. In fact, researchers have found no correlation between ALM and sun exposure.

ALM commonly develops in the following areas:

• The soles of the feet
• The palms of the hands
• Underneath fingernails, especially the thumbs
• Underneath toenails

Although rare, ALM affects people with darker skin more than others. Researchers are still trying to uncover why.

What Causes Acral Lentiginous Melanoma? 

Acral lentiginous melanoma begins when the skin’s melanocyte cells grow more quickly than normal, leading to the formation of tumors.

Melanocyte cells are skin cells that produce melanin, the pigment that gives skin its color. As melanocyte cells rapidly produce, it leads to skin spots that are darker than normal.

ALM may develop around an existing mole, but can also occur without association to a previous mole on the body.

Genetics may contribute to the risk of developing ALM. If you had a family member who was diagnosed with this type of melanoma, you could be at greater risk.

Can ALM Be Prevented? 

The exact cause of acral lentiginous melanoma is not yet known, so there’s no sure way to prevent it. Regular skin-checks, however, considerably increase the likelihood of survivability.

Because ALM is an aggressive, fast-growing cancer, early detection can be life-saving. In addition to monthly at-home skin checks, you should visit a dermatologist annually for skin cancer screening.

Who Is Most at Risk for Developing ALM?

ALM is rare, but it is the most common type of skin cancer in people with darker skin. While just 2-8% of the white population will be diagnosed with ALM, up to 60% of those who are Black or of Asian descent may develop acral lentiginous melanoma.

Men are more likely to have large growths at the point of diagnosis, although men and women are equally at risk for this rare skin cancer.

Researchers speculate ALM has a genetic basis. So, if someone in your family has had ALM, you may be more at risk.

How Is Acral Lentiginous Melanoma Diagnosed?

Due to the myth that people with dark skin cannot get skin cancer, melanomas are less likely to be diagnosed early in people with brown or black skin. Early diagnosis significantly increases the chance of survival. Melanomas are fast growing cancers that quickly invade deeper layers of skin and spread to other parts of the body.

Performing a monthly skin-check at home can help detect melanoma in the early stages. Look for oddly-shaped marks with irregular borders that differ from the surrounding skin in color or texture. Check toenails and fingernails for dark, narrow streaks or stripes. Remember to inspect areas not exposed to the sun such as the palms of the hands and soles of the feet.

In addition to at-home checks, see a dermatologist for annual skin cancer screenings. If your doctor finds something that seems suspicious, they will perform a biopsy to rule out skin cancer.

First, the area will be numbed with local anesthetic. Then, a small sample of skin will be removed for closer inspection under a microscope.

How is ALM Treated? 

Acral lentiginous melanoma is treatable. Survival rates increase if the cancer is detected earlier. Your treatment plan will include a combination of surgery and systemic treatment, depending on whether or not your cancer has metastasized.

Surgery will remove the cancerous lesion and adjacent cancerous cells. If your cancer has spread to nearby lymph nodes, those may also be removed.

Systemic treatments include chemotherapy or radiation. This step is necessary only when the cancer has begun to spread throughout the body.

ALM is more deadly than other types of cancer, but this may be because diagnosis tends to come late. With early detection and immediate treatment, the 5-year survival rates for Blacks, Hispanics and Asians are each above 70%.

Dr. Tatiana Sousa is a board certified dermatologist who completed her undergraduate degree in biology at the College of St. Elizabeth in Morristown, New Jersey. She earned her medical degree and completed her internal medicine internship at the University of Texas Medical Branch in Galveston, TX. Dr. Sousa went on to complete her dermatology residency at MetroHealth Medical Center in Cleveland, Ohio, where she served as chief resident in her final year.