Melanoma is a type of cancer, most often of sun exposed skin. However, melanoma can also occur in areas that have limited to no exposure to the sun. Acral melanoma (AM) sometimes called acral lentiginous melanoma, is a very rare form of cancer that affects the pigment-producing cells of the skin, known as melanocytes, on the soles of the feet, hands or under fingernails or toenails.
Acral melanoma accounts for only about 2-3% of all cases of melanoma in Australia. It is the most common form of melanoma in people of African and Asian descent.
Where does acral melanoma occur?
Acral melanoma can develop on the palms of the hands and soles of the feet as well as under the toenails and fingernails (also known as subungual acral melanoma).
What are the causes and risk factors of acral melanoma?
The underlying cause of acral melanoma is unclear. Sun exposure does not appear to be a risk factor in most cases. Risk factors identified in developing AM, include:
Although research has found an association with these factors, AM can occur in any person, regardless of race or without exposure to possible risk factors.
What are the signs and symptoms of acral melanoma?
Signs and symptoms of AM can vary depending on the location.
AM grows on the surface of the skin or under the nail bed before becoming invasive (going into deeper layers of skin). Because of the misconceptions that melanomas only occur in sun-exposed areas and that people of colour are not at risk for melanoma, these melanomas can be discovered later than other types, after they have invaded deeper layers of skin or spread to other areas of the body (metastasised).
How is acral melanoma diagnosed?
Acral melanoma is typically identified during a physical examination. Your doctor may use a dermatoscope to take a closer look at a suspicious spot and identify the characteristics of acral melanoma. If your doctor suspects a suspicious spot is an acral melanoma, you will require a biopsy to confirm the diagnosis. A small sample of cells will be removed from the affected area and examined under a microscope. If the suspicious spot is in an area that is difficult to biopsy, you may be referred to a specialist with expertise in the area, such as a plastic surgeon. For example, biopsies of an acral melanoma underneath the nail require removal of the nail.
If the result of the biopsy indicates acral melanoma, you may have further tests to find out more about the melanoma and if it has spread to your lymph nodes or other areas of your body. This may include imaging such as a CT scan, MRI, PET scan or a sentinel lymph node biopsy (procedure that identifies, removes and examines the closest lymph nodes to the melanoma that may contain melanoma cells).
Information describing the terminology used in melanoma diagnosis can be found here.
Genetic testing
Genetic testing on a sample of cancerous tissue from the acral melanoma or site of spread, looks for certain genetic mutations that are thought to ‘drive’ the growth of ocular melanoma. Knowing your ‘mutation status’ may help to inform future treatment options. The common genetic mutations are:
How is acral melanoma staged?
Staging refers to how limited or advanced the melanoma is at the time of diagnosis. The higher the stage, the further the melanoma has spread in your body. The stage you are diagnosed with will guide your treatment team to develop your treatment plan.
Factors involved in staging
The Breslow Scale is used to determine if the melanoma is thin, intermediate or thick:
The thickness will determine whether a sentinel lymph node biopsy is required. A Sentinel
Sentinel Lymph Node Biopsy is required in melanoma with a thickness of 1mm or greater.
Staging
To find out more about Acral melanoma staging, please see Help sheet- Levels and Stages
Note: The medical team will use the information about the stage of the melanoma to determine the best possible treatment. It is important to be aware that every patient is treated individually and not all patients with the same stage of melanoma at diagnosis will be treated the same way. There are other factors (such as the presence of genetic mutations, other health conditions) which will result in some patients with the same stage of melanoma being treated differently.
How is acral melanoma treated?
It is important to see a doctor who specializes in treating patients with your specific type of melanoma. Your GP or dermatologist can refer you to a center that treats acral melanoma. It is important to note that you may need to travel for treatment, depending on where you live (speak with your GP, the treatment center, the cancer council or the MPA telehealth nurse service to discuss possible travel and accommodation assistance).
Treatment options for acral melanoma will depend on the size, location and spread of the melanoma. Treatment options may include surgery, systemic therapy, radiotherapy or a combination.
Surgery – a wide local excision is the primary treatment for acral melanoma. It involves removing the melanoma and a margin of healthy tissue surrounding it. The skin on the palms of your hands and the soles of your feet has a different structure to the skin on other areas of your body. This can make surgery in these areas more difficult. As a result, you may need a reconstructive procedure, such as a skin flap or graft, as part of your surgical treatment. Surgery to treat subungual melanomas can be complex due to their location underneath the nail. In some cases, amputation of part of a finger or toe may be required. For some people, surgery may be the only treatment that is required.
Systemic treatment- systemic treatments are those that target the entire body, circulating through the bloodstream to kill cancer cells. Systemic treatment may be offered if your acral melanoma has spread to lymph nodes or organs. Systemic treatments may be used after surgery (called adjuvant therapy), or when acral melanoma has spread or cannot be surgically removed. Systemic treatment can include:
Radiotherapy- Sometimes, acral melanoma can be treated with radiotherapy, which uses x-rays to destroy cancer cells. You may have radiotherapy in addition to other treatments if your acral melanoma has spread.
Clinical Trials- clinical trials are medical research studies that aim to find a better way to manage a particular disease. Clinical trials are used to test new treatments to see if they are better than the currently available treatments. Clinical trials are part of best practice medicine and are one of many options for treatment. Your doctor may suggest that you should take part in a clinical trial as part of your treatment for ocular melanoma. You can read more about clinical trials at www.australiancancertrials.gov.au.
Note: It is important to work closely with a team of medical professionals, including a dermatologist, oncologist, and surgeon, to develop a personalized treatment plan that considers your individual needs and circumstances.
Questions to ask your doctor
How did I get acral melanoma?
Do I need a biopsy? What will that consist of? When will I know the results?
Is this related to cutaneous (skin) melanoma? Should you check the rest of my skin?
Has the melanoma spread?
What are the stages of acral melanoma? What is my stage?
If I need more tests, what will they be?
Should I get a second opinion or explore another treatment centre with more experience with acral melanoma?
How will this diagnosis affect my quality of life?
What is my prognosis?
Have you tested my melanoma for genetic mutations?
What are my treatment options?
Am I eligible for a clinical trial?
What are the side effects of the treatment you recommend?
Will I be able to continue my normal daily life?
What type of follow-up will I need?
What supports are available?
Having a rare melanoma can feel isolating. Additionally, treatment can be disfiguring or impact your quality of life in many ways. Here are some support options available:
Melanoma Patients Australia (MPA)–
Rare Cancers Australia- offer support (such as emotional, practical, and financial) as well as advocacy for rare cancers. www.rarecancers.org.au
Melanoma Institute of Australia (MIA)- offer information sheets on acral melanoma
International websites
Melanoma Research Alliance – https://www.curemelanoma.org/about-melanoma/types/acral-melanoma
AIM at Melanoma Foundation- https://aimatmelanoma.org
Melanoma Patients Australia recognises Aboriginal and Torres Strait Islander Peoples as the Traditional Owners and Custodians of Australia, and we acknowledge, respect and embrace their continued connection to land, waters and community. We pay our respect to all Aboriginal and Torres Strait Islander Elders past, present and emerging.
We recognise, value and celebrate diversity and act in the spirit of inclusion.
