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Acral Lentiginous Melanoma

Last updated Aug. 25, 2021

Reviewed by: Lester Fahrner, MD

Approved by: Krish Tangella MD, MBA, FCAP

Acral Lentiginous Melanoma (ALM) is an uncommon type of melanoma of skin that typically affects older adults in the 7th decade. The condition mostly affects the palms of the hands and soles of the feet.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Acral Melanoma (AM)
  • ALM (Acral Lentiginous Melanoma)
  • AM (Acral Melanoma)

What is Acral Lentiginous Melanoma? (Definition/Background Information)

  • A melanoma is a type of cancer that develops from cells, called melanocytes. Melanocytes are cells that produce melanin; the pigment that gives skin its color
  • Acral Lentiginous Melanoma (ALM) is an uncommon type of melanoma of skin that typically affects older adults in the 7th decade. The condition mostly affects the palms of the hands and soles of the feet
  • Melanomas, in general, are more common in light-skinned individuals than dark-skinned individuals. However, of the melanomas that occur in dark-skinned individuals, Acral Lentiginous Melanoma is the most common type
  • Acral Lentiginous Melanoma is diagnosed with the help of a biopsy. Once a definitive diagnosis has been made, the melanoma is surgically removed (excised). Depending on how far the condition has progressed, additional modes of therapy may be needed
  • The prognosis of Acral Lentiginous Melanoma is good when the diagnosis is made early; the prognosis gets poorer as the disease advances. In general, the prognosis of ALM is much worse compared to other malignant melanoma types affecting the skin

Who gets Acral Lentiginous Melanoma? (Age and Sex Distribution)

  • Acral Lentiginous Melanoma is typically diagnosed in adults over the age of 40 years, with a peak age in between 60-70 years
  • It can occur in younger adults and children as well, but is very rare
  • In general, melanoma also occurs more frequently in Caucasians, as compared to other races. However, of the different types of melanoma that can occur in dark-skinned individuals, Acral Melanoma occurs proportionately with a higher frequency in them
  • ALM accounts for approximately 5% of all diagnosed melanomas

What are the Risk Factors for Acral Lentiginous Melanoma? (Predisposing Factors)

The following factors increase the risk for Acral Lentiginous Melanoma:

  • Exposure to ultra violet (UV) rays is a major risk factor. UV rays are present in sunlight, and also in tanning lamps and beds
  • Nevus (medical term for a mole) is a non-cancerous pigmented tumor. While most nevi never become cancerous (or malignant), a small number of atypical/dysplastic nevi (moles with abnormal shape/borders/color) may turn cancerous. When such dysplastic nevi run in families, the condition is called dysplastic nevus syndrome. Individuals with this condition have a 10% increased risk of developing melanoma. Despite the above and irrespective of the condition, whether the nevi are present since birth, or are normal, or atypical; the higher the number of moles, the greater is the risk
  • Fair-skinned individuals are at a higher risk; more so those with freckles or those who develop sunburns easily
  • Previous history of melanoma or a history of melanoma in parents/siblings
  • An inherited condition called xeroderma pigmentosum, where the ability of the cells to repair sun-induced damage to genetic material is impaired
  • Weakened immune system, as a result of infections (such as HIV), medications (chemotherapy or immunosuppressants), and due to the presence of cancers (or lymphomas)

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acral Lentiginous Melanoma? (Etiology)

The potential cause of Acral Lentiginous Melanoma (ALM) includes:

  • Uncontrolled activity of oncogenes (rogue genes that promote cell growth and division) or depressed action of tumor suppressor genes (genes that normally keep a check on cell growth and division) is thought to play a role in the development of melanomas
  • About 50% of all melanomas have a mutation (change) involving the BRAF oncogene
  • UV-radiation induces damage to DNA (the genetic material that determines our traits and functions), which in turn may turn-on oncogenes, or turn-off tumor suppressor genes
  • In families with inherited melanomas, gene mutations that increase the risk for cancer are passed on from one generation to the next

Note: ALM can occur on non-hair-bearing skin areas (such as the mouth); in such cases, exposure to sunlight is not believed to be a causative factor.

What are the Signs and Symptoms of Acral Lentiginous Melanoma?

Acral Lentiginous Melanoma can develop from a pre-existing nevus (mole) or can arise as a brand new skin lesion. The signs and symptoms may include:

  • A pigmented area that is Asymmetrical in shape, whose Borders are irregular or ragged
  • A pigmented area that is not Colored uniformly, unlike a benign mole, which has an even distribution of shades
  • Any suspicious looking spot, whose Diameter is more than ¼ inches (6 millimeters)
  • Any suspicious looking spot that is Evolving, or changing in shape/color

These signs are often collectively referred to as the ‘ABCDE characteristics’ of melanoma, by physicians. (Source: The Skin Cancer Foundation, New York)

  • A suspicious looking spot or a ‘potential melanoma’ often differs in appearance from other benign moles on the body. This variability is sometimes called the ugly duckling sign by physicians (Source: The Skin Cancer Foundation, New York)
  • A suspicious pigmented area/spot showing a spread of color to the surrounding skin and with any swelling, redness or itching (due to inflammation). Such areas may also be scaly, or exhibit some oozing of fluid, or bleeding
  • In Acral Lentiginous Melanoma, the common body sites involved include the oral mucosa, palms and soles (the feet are more commonly involved than the hands), and the portion underneath the nails (subungual melanoma, which starts off as a streak showing in the nail plate, or bruise-like discoloration)
  • Melanoma involving the hands and feet may appear as a brown/black spot on the skin. When present underneath the nails, often the thumb or large toe is involved

How is Acral Lentiginous Melanoma Diagnosed?

A thorough history and a complete physical exam by a physician are crucial for the diagnosis of Acral Lentiginous Melanoma. This is followed by some tests which include:

  • Biopsy of skin: A sample of the skin, from any suspected area found on physical examination, is taken and examined under a microscope for signs of cancer by a pathologist. The types of biopsy performed include:
    • Excisional biopsy: After numbing the area with a local anesthetic, the entire mole is removed with a small border of surrounding skin. Where possible, this is the generally preferred method
    • Punch biopsy: After numbing the area with a local anesthetic, a circular blade is pressed into the skin around the suspicious area, and a round piece of skin removed. This type of biopsy is carried out, when the lesion (the suspicious area) is large in size
    • Incisional biopsy: After numbing the area with a local anesthetic, a portion of the tumor is removed using a surgical knife
    • Nail area biopsy: After local anesthetic is applied, a portion of, or all of the nail plate is removed and the area of living tissue with the pigment is biopsied
    • Sentinel lymph node biopsy: Performed to determine if the melanoma has spread to nearby lymph nodes. A dye is injected into the area from where the melanoma is removed. The first lymph node that takes up the dye is biopsied and examined for cancer cells, under a microscope
  • Sometimes, biopsy of other large lymph nodes in the area near the melanoma may be performed using fine needle aspiration cytology (FNAC) technique. In this, a sample of cells is removed from the mass, using a syringe with a hollow needle and then examined under a microscope
  • If the melanoma is suspected to have metastasized (spread) to internal organs, imaging tests such as X-ray, CT scan or MRI of the affected areas may be carried out
  • In rare cases, biopsies of areas other than skin may have to be done, when the primary source/origin of the tumor cannot be determined 

Note: Dermoscopic pigmentation pattern is helpful in distinguishing an Acral Lentiginous Melanoma and a benign acral nevus. In a benign acral nevus, the pigmentation is along the furrows of the skin markings. In early Acral Melanoma, the pigmentation is present on the ridges of the skin surface markings. It is important to note that such a dermoscopic examination is mainly performed by a trained healthcare professional.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acral Lentiginous Melanoma?

Early stage melanomas include melanoma in situ (confined to just the upper skin layer called epidermis) or locally invasive melanomas that have spread to the deeper layers of the skin. The more advanced cases of Acral Lentiginous Melanoma can metastasize beyond the skin, to lymph nodes and other organs. Organs that are commonly involved in metastasis include:

  • Lung
  • Liver
  • Brain
  • Bone
  • Gastrointestinal tract

How is Acral Lentiginous Melanoma Treated?

The choice of treatment for Acral Lentiginous Melanoma depends on how far the cancer has progressed. This is estimated through staging of the tumor. Some of the factors taken into consideration during staging include:

  • The thickness of the melanoma (also called Breslow’s measurement): Tumors can be thin, intermediate, or thick, depending on how deep into the skin they have penetrated. The thinner the tumor, the better the chances of a cure
  • Presence of any ulceration (open sores) of  the tumor surface
  • Spread of melanoma to lymph nodes or other internal organs

The melanoma is sorted into one of four stages depending on how far it has progressed, with I and II being early stages, III and IV being later stages, where melanoma has spread to sites beyond the skin. While early stage melanomas can be treated by surgery alone, the later stages of the disease often require a combination of treatment measures.

Treatment options for melanoma include:


  • Simple excision of the tumor along with some normal, non-cancerous skin at the edges (called margin). The width of the margin is based on the thickness of the tumor; as the thickness of the melanoma increases, the margin required increases as well
  • Mohs micrographic surgery:
    • Being used of late by some surgeons as an alternative technique to standard excision of melanoma
    • A thin layer of skin is removed and checked for cancer. This process is then carried out continuously, until a cancer-free slice of skin is obtained
    • This procedure using frozen section specimens is rarely used as a surgical treatment option for melanoma
    • Mohs micrographic surgery with immunohistochemical staining is a useful technique. It requires more time to perform than standard Mohs surgery
  • Lymph node dissection, in cases where the melanoma has spread to involve the nodes: Lymph nodes help in drainage of tissue fluid (lymph). However, removal of these nodes may therefore lead to a local build-up of lymphatic fluid causing swelling (lymphedema)


  • Drugs are used to kill the tumor cells, which may be given as oral pills, or injected into veins
  • Side effects of chemotherapy may include nausea, vomiting, hair loss, loss of appetite, diarrhea, and fatigue, increased risk of infection, mouth sores, or easy bruising, depending on the drug used
  • In cases, where the melanoma is advanced, but remains confined to an arm or leg; chemotherapy is only circulated through the affected limb, by a process called isolated limb perfusion


  • This therapy stimulates the immune system and involves the use of substances produced naturally by the body or such similar synthetics, made in a laboratory
  • Drugs used include, synthetic immune proteins and proteins that boost the immune system, called cytokines - interferon alpha or interleukin-2
  • Side effects of cytokines may include chills, fatigue, fever, headaches and muscle aches; while synthetic immune proteins may cause the immune system to start attacking other parts of the body

Targeted therapy:

  • It involves the use of drugs tailored to target the differences in a melanoma cell, as compared to a normal cell
  • Half of all melanomas involve a mutation in the BRAF gene. This is targeted by a drug vemurafenib
  • Side effects may include nausea, joint pain, fatigue, rash, itching, hair loss, sensitivity to the sun, and rarely heart rhythm abnormalities, liver abnormalities, severe allergic reactions, and severe skin or eye associated conditions

Radiation therapy:

  • This uses high-energy beams to kill cancer cells
  • Generally, this method is not used to treat the original melanoma, but often to relieve symptoms, when the melanoma has spread to other organs; or following lymph node dissection, where many nodes were found to be cancerous
  • The most common side effects is fatigue, but this resolves once the treatment is complete

How can Acral Lentiginous Melanoma be Prevented?

A few steps to help prevent Acral Lentiginous Melanoma may include:

  • Avoid direct exposure to UV rays and remain in the shade when possible
  • When heading out into the sun:
    • Slip on a shirt
    • Slop on some sunscreen. Sunscreens with SPF values higher than 30, and those offering broad spectrum protections (against UV-A and UV-B rays), are recommended. Apply an ounce to all exposed areas, 30 minutes before heading outdoors. Reapply every two hours, and also after excessive sweating
    • Slap on a hat
    • Wrap on sunglasses

This is encapsulated as the “Slip! Slop! Slap! Wrap” method for skin cancer prevention. (Source: The American Cancer Society, Atlanta)

  • Avoid tanning beds and sun lamps
  • Perform self-examination of your skin, from head to toe, once a month
  • Get a professional skin exam from a healthcare provider, once a year
  • All patients with melanoma should undergo skin examinations regularly even after treatment, at least once a year throughout their lives

Despite the above, currently, there are no effective preventative measures against melanoma affecting the oral cavity.

What is the Prognosis of Acral Lentiginous Melanoma? (Outcomes/Resolutions)

  • Individuals with early-stage Acral Lentiginous Melanoma, have better outcomes compared to those with more advanced melanoma, where the cancer has spread to lymph nodes or other organs
  • In general, the prognosis of Acral Lentiginous Melanoma is poorer than other malignant cutaneous melanoma types, on a same stage comparison basis. Melanoma of the oral mucosa has an even worse prognosis than ALM affecting the hands and feet
  • Nevertheless, the prognosis depends upon a set of several factors, which include:
    • Stage of tumor: With lower-stage tumors, when the melanoma is confined to site of origin, the prognosis is usually excellent with appropriate therapy. In higher-stage cancers, such as those with metastasis, the prognosis is poor
    • Overall health of the individual: Individuals with overall excellent health have better prognosis compared with those with poor health
    • Age of the individual: Older individuals generally have poorer prognosis than younger individuals
    • The size of the melanoma: Individuals with small-sized melanomas fare better than those with large-sized ones
    • Individuals with bulky disease have a poorer prognosis
    • Involvement of vital organs complicate the condition
    • The surgical resectability of Acral Lentiginous Melanoma (meaning, if the melanoma can be removed completely)
    • Whether the cancer is occurring for the first time, or is recurrent. Recurring cancers have worse prognosis compared to those that do not recur 
    • Response to treatment: Melanomas that respond well to treatment have better prognosis compared to melanomas that do not respond to treatment
    • Progression of the condition makes the outcome worse 
  • An early diagnosis and prompt treatment of the condition generally yields better outcomes than a late diagnosis and delayed treatment

Additional and Relevant Useful Information for Acral Lentiginous Melanoma:

  • New types of melanoma treatment are currently under study. These include vaccines and newer targeted therapies that work on altered genes, or proteins in melanoma cells
  • The ‘Slip-Slop-Slap campaign’ was initially launched in Australia, by Cancer Council Victoria in the 1980s, to promote awareness about skin cancer and methods for its prevention. This was then adopted in New Zealand as the ‘Slip-Slop-Slap-Wrap campaign’ (Source: The Wikipedia)

The following dermoscopic features help in distinguishing a benign acral nevus and Acral Lentiginous Melanoma.

  • Dermoscopic pattern of Acral Melanoma may be described as having the following features:
    • Abrupt edges
    • Blue-white veil
    • Irregular diffuse pigmentation
    • Parallel ridge pattern
    • Peripheral irregular dots and globules
    • Serrated pattern
  • In benign acral nevus, the following four dermoscopic patterns can be seen:
    • Parallel furrow pattern: Here, the melanocytic pigmentation is visible on the parallel sulci of the skin marking
    • Lattice-like pattern: Here, the melanocytic pigmentation follow and crisscross the skin markings
    • Fibrillar pattern: Here, the melanocytic pigmentation cross the skin markings diagonally
    • Non-typical pattern: Here, the melanocytic pigmentation varies and does not follow typical patterns described

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Jan. 5, 2017
Last updated: Aug. 25, 2021