Lentigo maligna melanoma: sun-damaged skin, symptoms, diagnosis and treatment

Melanoma starts when the pigment-making cells of the skin, the melanocytes, become cancerous and multiply in an uncontrolled way. The British Association of Dermatologists (BAD) explains that lentigo maligna is one type of the earliest stage of melanoma, called melanoma in situ. In situ means the cancer cells are confined to the top layer of skin, the epidermis, and have not begun to invade deeper layers.

Cancer Research UK uses the two terms as steps on one path. A lentigo maligna is a flat patch that grows outwards in the surface layers of skin, slowly, over several years. If it becomes a lentigo maligna melanoma, it starts to grow down into the deeper layers of skin and may also form lumps called nodules. Melanoma Focus describes lentigo maligna melanomas as beginning flat and looking like a large dark freckle, growing outwards and changing shape, and then possibly forming a lump.

This distinction explains why doctors take small, slowly changing patches seriously: the early form is highly curable, while the invasive form needs more extensive assessment.

BAD says the most important cause is exposure to too much ultraviolet light in sunlight, and that sunbeds also raise the risk. It is especially common in white-skinned people who live in or frequently visit sunny countries, and older people are most prone, especially those with multiple harmless darkened patches (solar lentigines, sometimes called age spots) on the face or the backs of the hands.

The risk increases if a family member has had melanoma, and people who have had one lentigo maligna melanoma have an increased risk of getting another. BAD says it is not hereditary, but is more likely with a close relative who has had melanoma, and that genetic factors are less likely than in other melanoma types because sun exposure is by far the most important risk factor.

Cancer Research UK says it is most common on the head and neck and in people who have spent a lot of time in the sun. Melanoma Focus adds that many people forget to protect the top of the head, face and tops of the ears, which can lead to cancer developing from repeated UV damage. It is seen most in fair-skinned people who tan poorly but also occurs in darker skin types, according to BAD.

BAD describes lentigo maligna as a long-standing brown patch, most commonly on the face, which slowly enlarges and develops darker areas. Most early melanomas of this kind cause no symptoms. If it is not treated, it could become hard and lumpy, bleed, ooze or crust. BAD notes that the usual ABCDE rules are less useful for lentigo maligna than for other melanoma types, and that it is usually an enlarging brown mark on the face that is larger or darker than other marks, but can rarely be skin-coloured or pink.

The NHS lists changes that deserve a GP visit: a mole that has changed size, shape or colour; a mole that is painful, itchy, inflamed, bleeding or crusty; and a new or unusual mark that has not gone away after a few weeks. Finding a melanoma as early as possible can mean it is easier to treat.

At the GP appointment the NHS says you will be asked about your health, family history and symptoms, the GP will look at the area and may take a photograph to send to a dermatologist (teledermatology), and an urgent referral may follow if cancer is suspected. The NHS stresses that an urgent referral does not definitely mean you have cancer.

The NHS says a specialist dermatologist will check your skin and ask about changes you have noticed, and may use a magnifying device to look at the skin more closely. BAD names this device a dermatoscope.

The definitive test is a biopsy. BAD says that this may involve removing the whole area under local anaesthetic (an excision) with the tissue sent to a laboratory, or taking a sample if the area is too large to remove easily (an incisional biopsy). The pathology report then guides the next step. The NHS says results usually take about 2 weeks but sometimes longer.

If an invasive melanoma is found, the NHS says you will usually need more tests, which may include scans, tests on the lymph nodes and blood tests, to find how deep the cancer is and how far it has spread. BAD notes that for lentigo maligna that is in situ, usually no other tests are needed.

BAD says the main treatment for lentigo maligna is surgical and that there is no other treatment of proven benefit. It is important to remove it with a rim of normal skin (an adequate surgical margin); if the whole area is not removed completely, some may develop into invasive melanoma. Depending on how much tissue was removed first time, a second operation to widen the margin may be needed, which makes the scar larger and occasionally needs a skin graft. The NHS also notes that a plastic surgeon may operate when the melanoma is in a visible area such as the face.

In selected cases BAD says Mohs surgery may be used, where abnormal cells are removed a layer at a time to limit the size of the wound. Where complete removal is not possible because of size or location, or in people for whom surgery is not suitable, alternatives such as imiquimod cream, freezing with liquid nitrogen or radiotherapy may be advised, but BAD says these are not used routinely because there is a higher risk of it coming back compared with surgery, and that laser treatment also carries a high risk of recurrence. BAD adds that factors such as age may make it desirable to avoid surgery and observe the area for change.

For lentigo maligna melanoma that has grown deeper, the NHS says surgery is the main treatment for melanoma, with radiotherapy, targeted medicines, immunotherapy and chemotherapy used in some situations, particularly if the cancer has spread.

BAD says the outlook for lentigo maligna is excellent and that it is very rare for them to come back because they were in situ and had no opportunity to spread. It says that people who have had a lentigo maligna surgically removed do not need follow-up visits with their specialist, and that you will usually be seen once after surgery and then discharged. For melanoma that is invasive, the NHS says there are regular check-ups during and after treatment.

Self-care is mostly about skin awareness. BAD suggests looking at all areas of your skin monthly for changes, protecting yourself from too much sun by covering up and using sunscreen, avoiding sunbeds, and sharing sun advice with relatives. The NHS advises staying out of the sun in the hottest part of the day (11am to 3pm in the UK), covering arms and legs, wearing a wide-brimmed hat and sunglasses, and using sunscreen with an SPF of at least 30 and at least 4-star UVA protection.

BAD also says having had a melanoma may affect life or health insurance, particularly for the first five years, though some insurers are more flexible when it was in situ and fully removed.

In the UK, a changing skin lesion is usually seen first by a GP, who can refer you urgently to an NHS dermatology service; BAD notes that you can be referred for free through the NHS. The NHS notes that a plastic surgeon may carry out surgery when the melanoma is in a visible area such as the face.

Some people choose a private dermatology appointment for quicker access to mole assessment. If you do, ask for the pathology report and any images to be shared with your GP so that your records stay in one place.