Precancerous conditions of the skin

Lentigo maligna is a very early form of melanoma skin cancer called melanoma in situ. Cancer cells are only found in the top or outer layer of the skin (epidermis). It tends to grow slowly. If lentigo maligna isn’t treated, it may become a type of invasive melanoma skin cancer called lentigo maligna melanoma. It could take 10 years or more to happen.

Some doctors describe lentigo maligna as a precancerous skin condition because the cancer cells haven’t grown into deeper layers of skin or surrounding tissue.

Lentigo maligna usually develops on areas of skin that are regularly exposed to the sun without protection, especially the face, head and neck. It most often happens in people in their 70s or 80s.

The main risk factor for lentigo maligna is too much unprotected exposure to the sun. Older age also increases your chance of developing lentigo maligna.

Lentigo maligna is usually a flat, tan or brown patch on the skin with an uneven border. It tends to slowly get bigger and grows outward across the surface of the skin (called radial growth). The patch can include many different colours, often darker colours. Lentigo maligna can also look like a freckle that changes in size, shape or colour.

If you have signs and symptoms or your doctor thinks you might have lentigo maligna, you will be sent for tests. Tests used to diagnose lentigo maligna may include:

• a skin exam, which may include a dermoscopy
• an excisional biopsy (a type of surgical biopsy), punch biopsy or shave biopsy

Treatment options for lentigo maligna include:

• wide local excision
• Mohs surgery
• imiquimod (Aldara, Zyclara), which is a cream put directly on the skin (called topical therapy)
• radiation therapy