Medications are available to control rosacea, and sun protection should be part of any treatment plan. It's important to treat symptoms continuously because, if the skin is badly inflamed, it can make removing a skin cancer more difficult and result in a higher risk of recurrence. As rosacea can mask skin cancer (even under a microscope), the doctor may need to perform multiple surgeries to ensure the whole tumour is removed.
Melasma is characterised by large brown spots on the skin, predominantly affecting women. It is triggered by UV exposure, pregnancy and other hormonal changes, making it harder to treat than other forms of hyperpigmentation. Given its colouring, skin cancer can hide in patches of melasma.
Melasma is often treated with lightening agents like hydroquinone, which can also lighten the appearance of a tumour and make the borders less distinct, making it harder to detect and treat. Removal of skin cancer on melasma-affected skin is generally the same as if it were on a clear part of skin, although determining the margins for excising the tumour can be more difficult. As a precaution, the doctor may remove more skin than usual.
Topical medications to treat melasma shouldn't interfere with skin cancer removal, but some advanced therapies (such as laser or chemical peels) should be avoided before, during and after the procedure. Sunscreen is an important therapy for melasma and can prevent the pigmented cells from appearing at all; it should be used head to toe.
What you can do
If you have one of these skin diseases, you don't inherently have an increased skin cancer risk, but it can make tumours harder to detect and treat. It's important that you visit your skin cancer doctor every 12 months for a full-body exam. In between visits, make sure you check your skin at home for any new or changing spots, and pay close attention to areas of inflamed or pigmented skin.