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Lentigo maligna melanoma

The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 21, 2021.

Melanoma, a type of skin cancer that affects pigment cells called melanocytes, has been on the rise for decades. Though it’s not the most common type of skin cancer, melanoma is the most dangerous due to its likelihood to spread to other areas of the body. Still, the overall prognosis is good: According to the National Cancer Institute (NCI), 93.3 percent of patients are still alive five years after they’re diagnosed with melanoma.

There are more than 30 different kinds of melanoma, according to research published in BMC Cancer. One type is lentigo maligna melanoma, which also has a high survival rate due to the fact that it’s often caught before it spreads.

What is lentigo maligna melanoma?

Lentigo maligna melanoma is a rare type of melanoma skin cancer, accounting for about 5 percent of all melanomas, according to the NCI. It’s also sometimes called Hutchinson’s melanotic freckle.

Melanoma in general is known for its tendency to grow and spread quickly, but lentigo maligna melanoma often behaves differently. This skin cancer typically affects older, fair-skinned people. When it develops, it tends to remain “in situ” in the same layer of skin—the epidermis—for a long time before it affects nearby tissue. In fact, a 2020 study in Melanoma Research found that it takes about 28.3 years on average for a precancerous lesion (called lentigo maligna) to turn into a cancerous lentigo maligna melanoma.

Lentigo maligna melanoma is one of the types of melanomas most closely linked to sun exposure over time—even more than other types of melanoma. Because of this, lentigo maligna melanoma typically develops on the head and neck—areas consistently exposed to the sun. It’s also a reason people tend to be older when diagnosed with lentigo maligna melanoma, since they’ve had more years to accumulate time under the sun.

Causes of lentigo maligna melanoma

Changes to the genetic material in your cells over your lifetime are the main cause of lentigo maligna melanoma. These are called gene mutations. You may inherit gene mutations from your parents, but in the case of lentigo maligna melanoma, they’re often due to chronic and cumulative exposure to the ultraviolet (UV) rays of the sun, as opposed to intermittent sun exposure.

Radiation from sunlight includes both UVA and UVB rays. In addition to causing wrinkles and sunburns, they may also affect your cells’ DNA. Ultraviolet radiation from the sun, especially UVB rays, may instigate small changes in genes and, as cells multiply and divide, they pass this genetic mutation onto other cells. In some cases, these genetic mutations lead to cancer.

Symptoms of lentigo maligna melanoma

If a lesion hasn’t yet grown into the surrounding layers of skin, it’s simply referred to as lentigo maligna. Once it becomes invasive, it’s called lentigo maligna melanoma.

Lentigo maligna tends to develop on sun-exposed areas of the skin, mostly appearing on the body on the:

  • Head
  • Neck
  • Face

Before progressing to a melanoma, a lentigo maligna may be:

  • Brown lesion
  • Smooth
  • Same texture as the surrounding skin
  • Bigger than 3 cm across

Once a lentigo maligna becomes invasive, it may:

  • Change color to dark brown or black
  • Have a blue-black raised portion
  • Be raised
  • Feel different from the skin surrounding it

Though there may be different symptoms for lentigo maligna before it progresses to melanoma of the skin, remember that it’s a slow-growing cancer. Even when it’s growing, it tends to grow outward for several years before invading nearby tissue. Lentigo malignas may remain precancerous for up to 50 years.

Lentigo maligna may look similar to benign (noncancerous) skin lesions, such as solar lentigo, or “liver spots,” which are harmless. If lentigo maligna is misdiagnosed as a benign or noncancerous condition, it may delay treatment.

Risk factors of lentigo maligna melanoma

Risk factors increase the chance that you’ll develop lentigo maligna melanoma. Knowing these risk factors may help you and your doctor discuss steps for cancer prevention.

The risk factors for lentigo maligna melanoma include:

  • Exposure to UV rays: Chronic and consistent exposure to the UV rays from sunlight may increase the risk of lentigo maligna melanoma.
  • Age: The average age that people are diagnosed with melanoma is 65, and lentigo maligna melanoma especially tends to be diagnosed in older adults.
  • Light skin: Fair skin with a tendency to burn rather than tan, skin prone to freckles, and/or skin with many moles are risk factors for melanoma.
  • Race: Melanoma can affect anyone, but white people are much more likely to develop it.
  • History of skin cancer: If you’ve had skin cancer previously, even a different type of skin cancer, the risk of developing melanoma is higher.

In order to prevent exposure to UV rays, the American Academy of Dermatology Association recommends wearing a broad-spectrum sunscreen (that provides protection from both UVA and UVB rays) with an SPF of 30 or greater whenever you’re outside—even on cloudy days. Applying sunscreen on the head, neck and ears is especially preventive for lentigo maligna melanoma.

How lentigo maligna melanoma is diagnosed

Due to the similarities between lentigo maligna and benign skin lesions like liver spots, accurate diagnosis is key.

Your care team may use a few different methods in combination to diagnose lentigo maligna melanoma. Dermoscopy is a noninvasive technique that allows your care team to look closely at the cells in your skin through a high-powered magnifying glass. In some cases, the instrument doesn’t even touch the skin. Your care team may be able to capture images during a dermoscopy, which can be helpful in seeing changes in the skin over time.

If your care team needs a more detailed view for diagnosis, they may also perform a reflectance confocal microscopy (RCM), which takes longer than a dermoscopy but is helpful in diagnosing lentigo maligna when a dermoscopy isn’t conclusive. An RCM is also a noninvasive procedure, allowing your care team to diagnose a lentigo maligna without needing to perform a biopsy—though you still may need a biopsy if your care team can’t perform a dermoscopy or RCM. Both a dermoscopy and an RCM help doctors know exactly where to perform surgery if they do diagnose a lentigo maligna.

How lentigo maligna melanoma is treated

The main treatment for lentigo maligna or lentigo maligna melanoma is to remove the lesion. However, as most lentigo malignas occur on the head or neck, there may be cosmetic implications, especially on the face. Ask your care team about surgical techniques or tools that may help minimize scarring and long-term damage to the skin in that area.

If surgery to remove a lentigo maligna isn’t possible, radiation tends to be the next treatment option. If both surgery and radiation aren’t possible, or aren’t recommended, a topical cream called imiquimod, which is also used for other types of skin cancers, may be a treatment option as well.

Survival rates for lentigo maligna melanoma

The survival rates for lentigo maligna melanoma are good, especially when diagnosed while it’s still localized to the tissue where it began. The five-year survival rate represents what percentage of people are still alive five years after a cancer diagnosis. For lentigo maligna melanoma, according to a 2016 study in BMC Cancer, the survival rates are:

  • 100 percent for local lentigo maligna melanoma that hasn’t spread from the site where it started
  • 73.2 percent for regional lentigo maligna melanoma that has spread to nearby tissues or lymph nodes
  • 26.1 percent for distant lentigo maligna melanoma that has spread to distant parts of the body

According to a 2020 review in StatPearls Publishing, the survival rate remains high, with 97.1 percent of people diagnosed with lentigo maligna melanoma still alive 10 years after diagnosis. These survival rates show that, though there may be challenges to treatment due to lentigo maligna melanoma being primarily found on the head and neck, treatment tends to be successful, and diagnosis doesn’t necessarily affect lifespan.

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