Actinic Keratosis (AK): Precancerous Sun Damage
Actinic keratosis is a skin lesion caused by cumulative exposure to ultraviolet (UV) radiation from the sun. These lesions are sometimes described as “precancerous sun damage” because they reflect changes in skin cells that may, in some cases, progress to squamous cell carcinoma (SCC).
Actinic keratoses are most common in people with fair skin and on areas that have been exposed to the sun over many years, such as the face, scalp, backs of the hands, and forearms. They usually develop at an older age but may appear earlier, depending on skin type and the extent of sun exposure.
It is important to emphasize that not every actinic keratosis will develop into cancer. However, the presence of these lesions indicates cumulative skin damage and warrants evaluation by a dermatologist, appropriate treatment, and follow-up when necessary.
What does actinic keratosis look like?
Actinic keratosis usually appears as a small lesion measuring less than one centimeter, with a rough texture, a pinkish or reddish color, and scale attached to the skin’s surface. The lesion may sometimes feel spiky or tender to the touch.
Because these lesions may be subtle and not easily visible, they are sometimes easier to feel than to see.
They occur mainly on areas that have been exposed to the sun over a long period, particularly areas of the scalp where the hair has become thin or has been lost.
Another significant risk factor is suppression of the immune system, for example following an organ or bone marrow transplant. In these situations, the lesions may be more numerous, and the risk of developing skin cancer is higher.
Is actinic keratosis a form of skin cancer?
Actinic keratosis is considered a precancerous lesion, meaning that changes have developed in the skin cells as a result of cumulative UV damage.
Under microscopic examination, cells with abnormal features, known as dysplastic cells, can be identified. These changes do not necessarily indicate invasive cancer, but they reflect a process that may progress in some cases.
The course of actinic keratosis is not uniform. Some lesions remain stable for a long time, some regress spontaneously but may reappear, and others become thicker or progress to squamous cell carcinoma (SCC).
It is not possible to predict with certainty which lesion will progress or when. Therefore, once actinic keratosis has been diagnosed, it is important to assess the overall condition of the skin and establish an appropriate treatment and follow-up plan.
More than an isolated lesion: What is field cancerization?
An important principle in the treatment of actinic keratoses is that these lesions do not usually occur in isolation. They are often part of an entire area of skin that has been exposed to the sun for many years and has accumulated cellular damage, including areas where no obvious lesions are yet visible.
This phenomenon is known in medical literature as field cancerization—an area of skin with precancerous damage.
This means that a particular area, such as the scalp, forehead, or forearms, may contain visible actinic keratoses alongside areas with early changes that cannot yet be seen.
Therefore, when numerous lesions are present within a defined area, treating each lesion separately with liquid nitrogen may not always be sufficient. In suitable cases, treatment of the entire field may be recommended to address both the visible lesions and some of the early changes in the surrounding skin.
What treatments are available for actinic keratosis?
The choice of treatment depends on the number and location of the lesions, the extent of skin damage, the patient’s medical condition, and personal preferences.
An isolated lesion or a small number of lesions can often be treated by freezing them with liquid nitrogen. When numerous lesions or a large field of sun-damaged skin is present, treatment of the entire area may be considered.
5% 5-Fluorouracil (5-FU) – A topical treatment that acts against cells with abnormal changes. In a large comparative study, this treatment demonstrated the greatest effectiveness among four methods evaluated for reducing multiple actinic keratoses on the head over a 12-month follow-up period. Treatment usually continues for several weeks and may cause a pronounced local reaction, including redness, burning, peeling, and sometimes crusting.
5% Imiquimod – A topical treatment that stimulates an immune response in the skin against abnormal cells. It can be applied at home according to medical instructions, and the duration of treatment varies depending on the formulation and protocol. Treatment may cause redness and a local inflammatory reaction, and occasionally flu-like symptoms.
Photodynamic therapy (PDT) – A treatment performed in the clinic. A light-sensitive substance is applied to the skin, after which the area is exposed to light of an appropriate wavelength. This treatment can cover a relatively large field of damaged skin and generally provides a good cosmetic result. It is relatively brief compared with prolonged courses of topical treatment, although it may cause pain or a burning sensation during illumination. In suitable cases, a daylight-based protocol may also be used and may be associated with less pain.
Other treatment options are also available, depending on the condition of the skin and the medical indications. Treatment is selected individually, taking into account its expected effectiveness, duration, potential side effects, and convenience for the patient.
Why is it important to treat the entire affected area?
When multiple actinic keratoses are present, treating the affected field of skin may significantly reduce the number of lesions, improve the skin’s texture and appearance, and reduce the overall burden of precancerous lesions.
There is also evidence that some treatments may reduce the risk of developing skin cancer in the future. However, the degree of risk reduction varies between treatments, and complete prevention of skin cancer cannot be guaranteed.
In addition to treatment, it is important to maintain appropriate sun protection and undergo skin examinations according to your individual level of risk.
A lesion that grows rapidly, becomes thicker, bleeds, develops an ulcer, or becomes newly tender should be examined by a dermatologist and may require a biopsy.
In summary
Actinic keratoses are a sign of cumulative sun damage and often appear as part of a larger area of skin affected by prolonged exposure to ultraviolet radiation.
Assessing the entire area of affected skin, selecting an appropriate treatment, and maintaining regular follow-up make it possible to treat existing lesions while also addressing damage in the surrounding skin.
If you have been diagnosed with actinic keratoses, it is advisable to consult a dermatologist about the treatment that is most suitable for you and the follow-up plan you may need.
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