You may have noticed brown spots on your head or face and assumed they were harmless age spots. However, these spots could potentially be lentigo maligna, an early form of melanoma. Lentigo maligna typically develops as a slow-growing lesion on the head, face, and neck. It has the potential to develop into an invasive form of melanoma known as lentigo maligna melanoma. While lentigo maligna melanoma is a less common form of melanoma — accounting for 4 percent to 15 percent of all melanomas — it requires careful monitoring and treatment to prevent progression.

In this article, we’ll discuss what causes lentigo maligna melanoma, who’s at risk, what it looks like, and how it’s diagnosed. We’ll also talk about treatments for lentigo maligna melanoma and the prognosis (outlook).

What Is Lentigo Maligna?

Sometimes referred to as Hutchinson’s melanotic freckle, lentigo maligna is an early form of melanoma. It typically begins as a slow-growing lesion on sun-damaged skin and can progress to lentigo maligna melanoma if left untreated. Like other types of melanoma, lentigo maligna is caused by mutations (variations) in melanocytes, the pigment-producing cells of the skin.

Also called “melanoma in situ,” lentigo maligna is diagnosed when cancer cells are confined to the epidermis (outermost layer of the skin). If the cancer cells penetrate deeper into the skin — into the dermis or beyond — the diagnosis changes to lentigo maligna melanoma, indicating invasive melanoma.

Lentigo maligna has a good prognosis because it grows very slowly. In fact, it can take between 10 and 50 years for lentigo maligna to develop into lentigo maligna melanoma.

Lentigo maligna melanoma is closely associated with sun exposure. As such, it’s usually found on sun-damaged skin of the head, face, or neck. It’s most often diagnosed in people over the age of 50, as they’ve had more sun exposure over their lifetimes than younger people. Unlike some other forms of melanoma, lentigo maligna melanoma is primarily associated with sun exposure rather than the number of moles a person has, although having more than 50 typical moles or many atypical moles (those that are larger in size and have irregular borders or uneven coloring) can also increase the risk.

How Does Lentigo Maligna Melanoma Develop?

Melanocytes are cells found beneath the epidermis and within hair follicles that give skin its color. Lentigo maligna melanoma develops due to genetic mutations in melanocytes that cause them to grow out of control.

Long-term exposure to ultraviolet (UV) radiation is the most common cause of the genetic changes that leads to lentigo maligna melanoma. UV rays from sunlight or indoor tanning devices (such as tanning beds or booths) can damage skin over time, leading to lentigo maligna melanoma.

The abnormal growth of melanocytes starts in the epidermis. When these melanocytes are found only in the epidermis, it’s called lentigo maligna. In between 5 percent and 20 percent of cases, the abnormal melanocytes grow into the deeper layers of the skin, becoming invasive melanoma. When this happens, it’s called lentigo maligna melanoma.

It’s important to note that not all cases of lentigo maligna will transform into lentigo maligna melanoma. When it does happen, this change occurs very slowly, taking about 28 years on average to progress to lentigo maligna melanoma.

Who Is at Risk for Lentigo Maligna Melanoma?

Several factors can increase the risk of developing lentigo maligna melanoma. These risk factors include:

• Frequent exposure to UV rays from the sun or other sources
• History of severe sunburns
• Fair skin that burns or freckles easily
• Older age (the average age of diagnosis is 65)
• History of skin cancer
• Suppressed immune system

Having these risk factors doesn’t guarantee a person will develop lentigo maligna melanoma, but it does increase the risk. Since lentigo maligna melanoma is closely linked to UV ray exposure, the American Academy of Dermatology recommends always wearing sunscreen with an SPF of at least 30 when outside, even on cloudy days.

What Does Lentigo Maligna Melanoma Look Like?

Lentigo maligna melanoma is usually found on areas of the body regularly exposed to the sun, including the head, neck, and face. It can look similar to other types of melanoma found on these body parts.

In the early stages, lentigo maligna may:

• Appear brown (usually uniform, but can have a mix of different colors) on lighter skin tones and as subtle change in pigmentation or a dark spot on darker skin tones
• Have a smooth texture, similar to the surrounding skin
• Be irregular in shape

When the condition progresses to lentigo maligna melanoma, the lesions may:

• Change in color to dark brown, black, or blue on lighter skin and dark, ashen, or as a loss of pigment on darker skin
• Change to a texture different from the surrounding normal skin
• Have a raised border
• Start itching, stinging, or bleeding

How Is Lentigo Maligna Melanoma Diagnosed?

Lentigo maligna melanoma is diagnosed by dermatologists (skin specialists) using several types of tests. Dermatologists will usually examine the skin in the clinic and take a biopsy (a sample of the affected skin) to examine under a microscope to make a diagnosis.

Noninvasive Tests

The first thing health care providers will do is visually examine the skin lesion. They will look for signs of melanoma, including irregular borders, color variation, and changes in texture. They may also use dermoscopy, a technique that involves using a handheld magnifying tool to closely inspect the skin. By looking at the surface of the skin with a dermatoscope, health care providers may be able to tell the difference between lentigo maligna melanoma and other skin conditions.

A second test used to diagnose lentigo maligna melanoma is called reflectance confocal microscopy (RCM). This test uses a laser and a special type of microscope to look below the surface of the skin without needing to cut into it. RCM can also help determine where the edges of the lentigo maligna melanoma lesion are before treatment. However, RCM is a very specialized test and isn’t available in all dermatology clinics.

Excision Biopsy

If a health care provider thinks that a skin lesion looks like lentigo maligna melanoma, they’ll usually cut it out. This is called an excision biopsy. A pathologist (specialist in examining tissue samples) will then look at the biopsy using a microscope. They’ll look for signs of cancer and determine how deep the cancer cells have spread.

In cases where the skin lesion is large or located in delicate areas such as the face, health care providers may opt for a partial biopsy, removing only a smaller portion of the affected skin. However, diagnosing lentigo maligna melanoma may be more difficult with a partial biopsy, given the limited amount of tissue being analyzed.

Lentigo maligna melanoma can be classified into stages based on if the cancer has spread from where it started. These stages are numbered 0 to 4 (sometimes rendered with Roman numerals, e.g., “stage III” instead of “stage 3”). Stage 0 represents lentigo maligna, and stage 4 represents lentigo maligna melanoma that has spread to other parts of the body. The thicker the melanoma is, the more likely it is to metastasize (spread to other parts of the body).

What Are the Treatment Options for Lentigo Maligna Melanoma?

Like other melanomas, the main treatment for early-stage lentigo maligna melanoma is usually surgery. However, there are other options if surgery can’t be used or doesn’t work.

Surgery

The goal of surgery is to remove the entire lentigo maligna or lentigo maligna melanoma lesion. This is typically done through surgical excision, where the lesion is cut out. Doctors aim for surgical margins of 5 to 10 millimeters around the lesion. This means they want to remove a small area of healthy skin around the melanoma to ensure they remove all the cancer cells. The amount of healthy skin removed depends on the depth and extent of the lesion.

Other Treatment Options

When the lesion is large or located in an area where surgery could cause significant cosmetic issues (such as on the face), alternative treatments may be considered. The next common treatment for lentigo maligna melanoma is usually radiation therapy. Other options include cryotherapy (using extreme cold to treat the skin lesion) or a topical (applied to the skin) cream called imiquimod.

However, these treatments are less likely than surgery to cure lentigo maligna melanoma and are considered nonstandard options.

For more advanced cases of lentigo maligna melanoma where surgery and local treatments aren’t an option, alternative treatments include immunotherapy, targeted therapy, and, in some cases, chemotherapy.

Follow-Up

After treatment, your dermatology or oncology team will likely recommend regular follow-up appointments. These visits help determine if the treatment was successful and detect any new lentigo maligna melanoma lesions. This is particularly important because lentigo maligna melanoma has high recurrence rates (likelihood of the cancer returning), with up to 20 percent of cases returning after treatment.

What Is the Prognosis for Lentigo Maligna Melanoma?

The term “five-year survival rates” refers to the percentage of people who are alive five years after diagnosis. The five-year survival rate for lentigo maligna melanoma depends largely on whether or not the melanoma has metastasized. The rates are as follows:

• Stages 1 and 2 — More than 99 percent of people diagnosed with early-stage lentigo maligna melanoma are alive five years after diagnosis.
• Stage 3 — When lentigo maligna melanoma has spread to nearby tissues or lymph nodes, the five-year survival rate is around 74 percent
• Stage 4 — When lentigo maligna melanoma has metastasized to distant parts of the body, the five-year survival rate is around 35 percent

Other factors that can affect the outlook for lentigo maligna melanoma, including a person’s overall health and immune system status. Early detection and treatment also play a crucial role in improving survival outcomes.

Talk With Others Who Understand

MyMelanomaTeam is the social network for people with melanoma and their loved ones. On MyMelanomaTeam, more than 1,000 members come together to ask questions, give advice, and share their stories with others who understand life with melanoma.

Have you or a family member been diagnosed with lentigo maligna or lentigo maligna melanoma? What signs did you notice? Share your experience in the comments below, or start a conversation by posting on your Activities page.