Lentigo maligna and melanoma in situ are the very earliest stage of a skin cancer called melanoma.
The word ‘melanoma’ comes from the Greek word ‘melas’, meaning black. Melanin is the dark pigment that gives the skin its natural colour. Melanin is made in the skin by pigment cells called melanocytes. After our skin is exposed to sunlight, the melanocytes make more melanin, and so the skin becomes darker.
Melanocytes sometimes grow together in harmless groups or clusters, which are known as moles. Most people have between 10 and 50 moles and often they are darker than the surrounding skin.
Melanomas can arise in or near to a mole, but can also appear on skin that looks quite normal. They develop when the skin pigment cells (melanocytes) become cancerous and multiply in an uncontrolled way. They can then invade the skin around them and may also spread to other areas such as the lymph nodes, liver and lungs.
‘In situ’ means that the cancer cells have not had the opportunity to spread to anywhere else in the body. There are cancer cells in the top layer of the skin (the epidermis) but they are all contained in the area in which they began to develop. They have not started to spread or grow into deeper layers of the skin and have not become invasive. This is why some doctors call in situ cancers ‘pre cancer’. The prognosis is excellent.
Lentigo maligna is a type of melanoma in situ. It is a slow growing lesion that appears in areas of skin that get a lot of sun exposure, such as the face or upper body. Because it grows slowly it can take years to develop. Similar to melanoma in situ, lentigo maligna has not spread and is only in the top layer of skin.
Both melanoma in situ and lentigo maligna are cured with surgery. However if not treated with appropriate surgery, they can develop into an invasive cancer. This is why it is important to have them removed with an adequate surgical margin and to know about preventative measures you can take which will lower your risk of these conditions occurring again in the future.