Section Editor: Allison Osmond MD FRCPC
June 13, 2026
Lentigo maligna is a type of melanoma in situ, a very early form of skin cancer that has not yet spread beyond the top layer of the skin (the epidermis). It develops in skin that has had years of sun exposure, such as the face, neck, and arms, and it usually affects older adults. Lentigo maligna grows very slowly and can remain in this early, noninvasive stage for years before progressing to invasive melanoma, called lentigo maligna melanoma.
This article explains what a diagnosis of lentigo maligna means, what the findings in your pathology report describe, and how those findings guide the decisions you and your doctor make together. Because lentigo maligna is confined to the skin’s surface, the outlook is excellent, and treatment aims to remove the lesion before it has a chance to become invasive.
What causes lentigo maligna?
Lentigo maligna is caused mainly by long-term exposure to ultraviolet (UV) light, usually from the sun, which damages the DNA of the melanocytes, the pigment-producing cells of the skin. People with lighter skin, a history of significant sun exposure, or frequent sunburns are at higher risk. The risk increases with age and is greatest in people over 50. A weakened immune system or a personal history of skin cancer also raises the risk.
What are the symptoms of lentigo maligna?
Lentigo maligna usually appears as a flat or slightly raised patch of discolored skin. Common features include a brown, black, or tan patch that may have lighter and darker areas, an irregular shape with uneven or blurred borders, and slow growth over time. The patch may feel slightly rough but usually does not cause pain, itching, or bleeding. Because lentigo maligna can look like a harmless age spot or freckle, it is important to watch for changes in size, color, or shape and to see a doctor if these occur.
What is the difference between lentigo maligna and lentigo maligna melanoma?
Lentigo maligna is an early form of melanoma confined to the epidermis and not invading deeper layers or spreading elsewhere. Lentigo maligna melanoma develops when the cancer cells grow downward into the dermis, the thicker layer beneath the epidermis. This downward growth marks the change to invasive melanoma, which has the potential to metastasize (spread) to other parts of the body. Removing lentigo maligna while it is still confined to the epidermis prevents this from happening.
How long does it take for lentigo maligna to turn into melanoma?
Lentigo maligna grows very slowly and can stay in the in situ stage for months or even years before progressing to lentigo maligna melanoma. The time it takes varies widely from person to person, and not every lentigo maligna will become invasive. Regular monitoring and early treatment greatly reduce the risk of progression.
How is the diagnosis made?
The diagnosis is made after a skin biopsy, in which a sample of the suspicious area is removed and examined under the microscope by a pathologist. Before the biopsy, a doctor may use dermoscopy (a way of examining the skin under magnification) to look for characteristic features. Under the microscope, the pathologist looks for abnormal melanocytes that are larger, darker, and more irregular than normal and that are confined to the epidermis, spread out along its bottom (basal) layer. Some abnormal melanocytes may extend upward into the deeper layers of the epidermis, a pattern called pagetoid spread. The dermis underneath almost always shows solar elastosis (sun damage to the connective tissue), and a small amount of inflammation may be present. Examining the tissue also allows the pathologist to rule out harmless spots that may look similar, such as age spots. Because the changes can be subtle and the abnormal cells often extend beyond what is visible to the naked eye, the pathologist may use special stains to highlight melanocytes and assess how far they extend.
Surgical margins
A margin is the edge of the tissue removed during surgery. The margin status indicates to you and your doctor whether the entire lesion was removed. Margins are especially important in lentigo maligna because the abnormal melanocytes often extend well beyond the visible edge of the patch, making complete removal difficult.
- Negative margin — No abnormal melanocytes are seen at the cut edge, which suggests the lesion was completely removed. The pathologist often also measures the distance from the nearest abnormal cells to the edge.
- Close margin — Abnormal melanocytes are near the cut edge but do not reach it. Depending on the distance, more surgery may be considered.
- Positive margin — Abnormal melanocytes are present at the cut edge, which means some of the lesion may remain. A positive margin is associated with a higher likelihood that the lesion will return and usually leads to further treatment.
What is the prognosis?
The outlook for lentigo maligna is excellent when it is found and treated early. Because it is confined to the top layer of the skin, it can usually be removed completely, and once it is removed, the chance of it coming back is low. Lifelong skin monitoring is still recommended, both to watch for recurrence and to check for new lesions, because people with lentigo maligna have sun-damaged skin and a higher risk of other skin cancers. If lentigo maligna is not fully removed or is left untreated and progresses to lentigo maligna melanoma, the outlook then depends on the depth of invasion and whether the melanoma has spread.
What happens after this diagnosis?
The main treatment for lentigo maligna is surgical removal of the lesion with a margin of normal skin. Because the abnormal cells often extend beyond the visible patch, the surgeon may use a wider margin or a margin-controlled technique, such as staged excision or Mohs micrographic surgery with special stains, to confirm that all of the abnormal cells have been removed. These approaches are especially useful on the face, where preserving healthy tissue matters. When surgery is difficult or not possible, other options that your doctor may consider include radiation therapy and a topical immune-activating cream applied to the skin over several weeks.
After treatment, regular skin examinations are important to monitor for recurrence and new lesions, and protecting the skin from further sun exposure is a key part of long-term care. Care is usually coordinated by a dermatologist, sometimes together with a surgeon (such as a Mohs surgeon), a radiation oncologist, and the pathologist who made the diagnosis.
Questions to ask your doctor
- Was the lentigo maligna completely removed, and were the margins clear?
- If the margins were positive, what are my options?
- Was there any sign that the lesion had become invasive (lentigo maligna melanoma)?
- Because lentigo maligna can extend beyond what is visible, would a margin-controlled technique such as staged excision or Mohs surgery be better for me?
- If surgery is difficult, would radiation or a topical cream be an option?
- How likely is this to come back?
- How often should I have follow-up skin checks?
- Am I at higher risk of developing melanoma elsewhere on my skin?
- What can I do to protect my skin from further sun damage?
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