Lentigo Maligna

| 10 min read

Although lentigo maligna is not dangerous in itself, further treatment is often advised because (i) it carries a risk of developing into melanoma – a serious form of skin cancer that has the potential to spread elsewhere in the body and (ii) because we have only sampled part of the pigmented area and we cannot totally exclude the possibility that this progression to melanoma has not already happened elsewhere within the affected area.

There are a number of treatment options with advantages and disadvantages. It is important to be aware that Lentigo maligna can sometimes spread much further on the skin surface than is visible and complete surgical removal can lead to a large defect (hole) requiring reconstructive surgery. For this reason surgical treatment is not the right option for all patients.

Treatment options include:-

• Doing nothing (conservative management): In this scenario the area would be monitored by examination on a regular basis and treatment would be performed if there is a change in appearance. The major disadvantage is that if progression to melanoma occurs, this may be detected at a later stage when it may have already spread or may be harder to treat.
• Confocal microscopy: This is a non-invasive skin microscope that can give more information about how far the lentigo maligna has spread across the surface. It can also be used for monitoring of the area if no treatment is performed. It is not as accurate as a surgical biopsy in diagnosing the size of the affected area or in ruling out cancerous change.
• Topical treatment: A cream (imiquimod) can be applied (usually for a minimum of 2 months). In some cases this will stimulate the immune system to remove the lentigo maligna. If it is effective there will be a severe infammatory reaction lasting for several weeks at least. Disadvantages are that it is signiHcantly less effective than surgical treatment and it can be difficult to know whether the condition has been fully treated or whether it recurs in the future. You can learn more about this treatment at the following link: Imiquimod
• Wide local excision: The affected area is removed with a margin (usually 5mm) and sent for analysis. The defect (hole) created is then repaired by reconstructive surgery. An advantage is that the entire area is analysed. A disadvantage is that further treatment may be needed if the lentigo maligna has spread further on the surface of the skin or if analysis of the sample reveals evidence of progression to melanoma.
• Mohs surgery: The affected area is removed with a margin under local anaesthetic and sent for analysis but rather than repairing the defect immediately the results of the microscope analysis are awaited (usually takes 48 hours) and then used to guide whether additional areas of skin need to be taken. Often several procedures are required over 1-2 weeks (with a dressing left in place in between). Advantages are that the lentigo maligna can be fully removed. A disadvantage is that the Hnal defect may be much larger than is seen on the skin surface. Another disadvantage is that this procedure is logistically complex requiring processing of pathology samples and multiple Mohs procedures in a week. Because of this, although we perform it routinely within the NHS at Guy’s hospital and I perform Mohs surgery for other conditions privately, due to these logistical issues

You can also read more about lentigo maligna at the following link: Information leaflet