Lentigo Maligna

Overview

Lentigo maligna is a very early form of melanoma in which the cancerous cells are still confined to the outermost layer of the skin (the epidermis). It is sometimes called melanoma in situ, meaning "in place," because it has not yet grown into the deeper layers. It appears as a flat, irregular brown or tan patch that slowly enlarges over years.

Lentigo maligna most often develops on chronically sun-exposed skin, particularly the face, in older adults. If left untreated, it can eventually progress to an invasive melanoma called lentigo maligna melanoma, which can spread. Because it is caught at an early, treatable stage, recognizing and removing lentigo maligna offers an excellent chance of cure.

Symptoms

Lentigo maligna usually appears as a slowly changing skin patch with features that distinguish it from a harmless age spot or freckle:

• A flat, brown or tan patch, often with darker or lighter areas of color
• An irregular, poorly defined border
• Slow growth and gradual enlargement over months to years
• Variation in color, sometimes including brown, black, or reddish tones
• Location on sun-exposed skin, especially the face, ears, neck, or arms

The classic warning signs of melanoma, summarized as ABCDE (Asymmetry, Border irregularity, Color variation, Diameter, and Evolving or changing), apply. Any new or changing pigmented patch should be examined by a doctor.

Causes

Lentigo maligna develops when pigment-producing skin cells (melanocytes) become abnormal, driven largely by long-term damage from ultraviolet (UV) light. Contributing factors include:

• Chronic sun exposure: Years of cumulative UV exposure from sunlight is the main driver.
• Sun damage: It typically arises on skin already showing signs of long-term sun damage.
• Aging skin: Risk increases with age as sun damage accumulates.

The damage causes melanocytes to grow abnormally within the top layer of skin. Over a long time, some of these cells may become invasive.

Risk Factors

• Older age
• Fair skin that burns easily
• A history of significant or chronic sun exposure or sunburns
• Lots of sun damage, such as freckling and age spots on the face
• A personal or family history of melanoma or other skin cancers
• A weakened immune system

Diagnosis

A dermatologist evaluates a suspicious patch using clinical examination and a skin biopsy:

• Skin examination and dermoscopy: Inspecting the patch closely, often with a handheld magnifier (dermatoscope), to assess its features.
• Skin biopsy: Removing a sample of the skin (or the whole lesion) so it can be examined under a microscope, which confirms the diagnosis and shows whether it remains in situ or has become invasive.

Treatment

Because lentigo maligna can progress to invasive melanoma, it is usually treated even though it is an early lesion:

• Surgical removal: The main treatment, removing the lesion along with a margin of normal skin. Techniques that carefully check the edges are often used, especially on the face.
• Other options: When surgery is not suitable, alternatives such as certain topical medications or radiation therapy may be considered, though surgery is generally preferred.
• Ongoing skin checks: Regular monitoring for recurrence or new skin cancers.

Caught early and fully removed, lentigo maligna has an excellent outlook. Once it becomes invasive, treatment follows that for melanoma.

Prevention

• Protect skin from the sun with shade, clothing, and a wide-brimmed hat
• Use broad-spectrum sunscreen and reapply as directed
• Avoid tanning beds and intense midday sun
• Check your skin regularly for new or changing spots
• Have regular skin examinations if you are at higher risk

When to See a Doctor

See a doctor or dermatologist promptly if you notice a pigmented patch that is new, enlarging, or changing, particularly on sun-exposed skin. Be especially alert to a spot that:

• Is asymmetric or has an irregular, blurred border
• Has uneven color or multiple shades
• Is growing, especially if larger than a pencil eraser
• Is changing in size, shape, or color over time

Early evaluation is important because lentigo maligna is highly treatable when caught at an early stage.

Related Topics

Frequently Asked Questions

References

1. American Academy of Dermatology Association. Melanoma.
2. National Cancer Institute (NCI). Melanoma Treatment.
3. Mayo Clinic. Melanoma — Symptoms and causes.
4. Skin Cancer Foundation. Melanoma.