Actinic keratosis vs skin cancer: how they are related

Actinic keratoses (also called solar keratoses) and non-melanoma skin cancer share a cause. The British Association of Dermatologists (BAD) says actinic keratoses are caused by sun exposure over many years, including sunbathing, sunbed use, outdoor work and recreation, and living in a sunny country. The NHS says ultraviolet (UV) light, from the sun and from sunbeds, is the most common cause of non-melanoma skin cancer.

In that sense an actinic keratosis is a marker of skin that has been damaged by the sun. The BAD says the presence of actinic keratoses indicates sun damage to the skin, and that people affected by many of them are also at higher risk of developing other types of skin cancer compared with someone of the same age without them. The NHS says it is not usually serious, but there is a small chance the patches could become skin cancer.

Non-melanoma skin cancer, by contrast, is a cancer. The NHS says the main symptom is a growth or unusual patch on the skin. The BAD names squamous cell carcinoma as the form of skin cancer an actinic keratosis can progress to.

The table summarises the descriptions given by the NHS and the BAD. Appearance varies, and the descriptions overlap, which is exactly why a clinician needs to look.

The key is change. The NHS says you should see a GP if you notice new patches on your skin, or if existing patches begin to bleed, get bigger, change colour, feel tender or develop into a lump. It also says to see a GP if a patch appears on your lips. These are the changes that might indicate something more serious such as skin cancer.

The BAD uses similar wording: if an actinic keratosis develops into a lump or horn, grows very quickly, becomes tender, forms an ulcer or starts to bleed, it is important to seek medical advice, because these changes could indicate the early onset of skin cancer.

The NHS symptom page for non-melanoma skin cancer gives the other side. See a GP if you have a growth on your skin that is getting bigger or has changed colour or texture, or a growth or area of skin that hurts, itches, bleeds, crusts or scabs for more than 4 weeks. It also notes that a new mole or change in an existing mole may be a sign of melanoma, a more serious type of skin cancer, and that this needs separate attention.

The BAD says that usually the appearance of an actinic keratosis is enough for a doctor who manages skin problems, such as a GP or dermatologist, to make the diagnosis. In cases of uncertainty, a sample (biopsy) or the whole affected area may be removed under local anaesthetic and examined under a microscope in the laboratory. Surgical removal also provides a sample for the laboratory, which confirms the diagnosis.

The NHS says that for suspected non-melanoma skin cancer the GP will look at the area, ask about your health, your symptoms and how much time you spend in the sun, and may ask to take a photograph to send to a specialist (a dermatologist). You may get an urgent referral for more tests or to see a specialist, which the NHS says does not definitely mean you have cancer.

For actinic keratoses, the NHS says that if you have only one patch a GP might suggest waiting to see if it goes away on its own, while more than one patch or a patch that causes problems such as pain or itching usually warrants treatment, and a GP may refer you to a dermatologist. The listed treatments are prescription creams and gels, freezing (cryotherapy), surgery to cut out or scrape away the patches under local anaesthetic, and photodynamic therapy (PDT).

The BAD adds that some actinic keratoses may go away without treatment, especially small ones when the skin is protected from the sun, that cream treatments often cause temporary redness and soreness, that cryotherapy does not normally leave a scar but can lighten the skin permanently, and that some people choose to monitor their skin instead. It also says actinic keratoses can be treated but tend to recur over time.

Treatment for non-melanoma skin cancer is arranged by specialists after diagnosis and is outside the scope of this comparison.

The advice is the same for both conditions. The NHS says to check your skin regularly for changes, use sunscreen with a sun protection factor (SPF) of at least 30 and reapply regularly, wear a hat and clothing that covers arms and legs, and avoid sunbathing, sunlamps and sunbeds. It also advises keeping out of the sun between 11am and 3pm, when it is strongest. The BAD says to avoid sunburn, that even a tan is a sign of skin damage, and that no sunscreen can offer 100% protection, so sunscreen should supplement clothing and shade, not replace them.

The NHS notes that if you always cover up outdoors you could consider taking 10 micrograms of vitamin D a day, because you may not get enough from sunlight.