Actinic (solar) keratosis

Never go out of the house without appropriate sun protection! Avoid the midday sun! Sunscreen alone is not enough, protect your skin with appropriate clothing! Stay in the shade at all costs!

There are many tips for proper sun exposure, some of which are limiting. What could be so bad about lying in the sun for a few hours? The worst case scenario is that you get a little sunburn. And even if it is unpleasant, it usually goes away in a few days.

The consequences of sun exposure

But the warnings are definitely appropriate: There are several diseases that develop only because there is not enough sun protection. Most feared is skin cancer, but even preliminary stages of it are troublesome and also dangerous. Thus, the lack of protection against sun radiation frequently leads to actinic keratosis, a cornification disorder caused by light damage.

Actinic keratosis as skin cancer precursor

Actinic or solar keratosis itself is relatively harmless. Nevertheless, the skin disease is not harmless as it is a preliminary stage of the so-called prickle cell skin cancer which is called spinalioma in medicine. Especially with increasing age it becomes more and more likely that a cancer develops from the harmless actinic keratosis.

Distribution of actinic keratosis

Actinic keratosis occurs mainly in fair-skinned people with blond or red hair, because they have few pigments in their skin that would protect them from the sun's rays.

However, it takes years or even decades for the skin to be damaged enough for the keratinization disorder to develop. This is why actinic keratosis usually only occurs after the age of 50.

Men in particular are frequently affected by the disease, as they often work outdoors. During this time, the skin is rarely sufficiently protected.

The cause for the development of solar keratosis is UVB radiation, which is emitted by the sun. Especially years of unprotected irradiation with UVB rays trigger a mutation in the cells of the skin. This is a minimal change in the genetic material, or DNA, of the cells.

DNA damage alters cell cycle

The damage to the genetic material of the skin cells changes the life cycle of the skin cells. Normally, they develop, then perform their function for a period of time, and then die, sending themselves into cell death. Controlled cell death is one of the most important mechanisms to prevent tumors.

Mutations in the DNA can destroy this mechanism. Then the cells continue to live, although they no longer function properly, because they are simply already too old. The mutations can also cause the cells to multiply more quickly, and the skin layer becomes increasingly thicker as a result.

Cancer development only decades later

Many years or even decades after the cells have been damaged, the rapid growth of the degenerated cells begins. If these then also penetrate into other tissues, i.e. do not only remain in the upper skin layer, then one speaks of a spinalioma. Every fifth to tenth actinic keratosis develops into this skin cancer in the course of time.

Solar keratosis develops mainly on the skin areas that are particularly exposed to the sun. These are located on the face, forehead, temple, bald neck and neckline. The backs of the hands and forearms are also often affected. In men, the skin change is mainly found on the bald head or at the light hairline, as these areas of the skin are rarely protected from the sun.

Skin patches with yellowish-greyish-brown discolouration

Actinic keratosis appears as skin patches which are reddish in colour and have a rough surface in the early stages. Over time, the affected horny layer becomes thicker and the spots turn yellowish-greyish-brown.

In addition, the affected areas are very sensitive and the skin is quickly injured. Frequently, several foci develop at once, which can reach a diameter of several centimetres.

Very discrete symptoms

In general, the changed skin areas are often not very noticeable, as they do not cause any discomfort. Neither an itching nor a burning sensation indicates that the skin has changed pathologically. This is aggravated by the fact that the skin patches in actinic keratosis develop only very slowly and leisurely.

For the diagnosis of actinic keratosis, a small sample must be taken and examined histopathologically. Here, the sample is processed in such a way that it can be viewed greatly magnified under a microscope.

This is the only way to confirm the diagnosis. This is because solar keratosis is in no way different from skin cancer in terms of appearance alone. But it is of course of special importance that the distinction can be made.

The therapy to be applied depends primarily on the size and frequency of the affected skin areas. Their location is also crucial, as not every therapy method can be applied everywhere. The most important therapeutic approaches include:

• surgical removal
• cryotherapy (icing with liquid nitrogen)
• laser therapy (ablation with a strong laser)
• curettage (removal with a sharp spoon)
• chemical peeling (application of a corrosive solution)
• chemotherapy (application of a cytostatic ointment)
• diclofenac hyaluronic acid therapy

Photodynamic therapy

A new therapy that is popular today is photodynamic therapy (PDT). Here, a photosensitive drug is taken which initially has no effect on the body. Only when it is activated at the affected areas with a laser does the effect take place and the actinic keratosis is removed. After only a few days, the affected areas heal without scarring.

If actinic keratosis is regularly controlled and treated, the prognosis is very good. However, close monitoring must be carried out to be able to prevent the development of skin cancer, or at least to detect it at an early stage.

High risk of developing skin cancer

If you have more than ten areas of skin affected by actinic keratosis, the risk of developing skin cancer within the next five years is significantly increased. The downside, however, is that it can never be said which of the skin patches will turn malignant, so you don't know which areas will need to be ablated to prevent degeneration.

It should be noted that cancer does not always form. Sometimes the skin patches simply remain affected by solar keratosis, sometimes the change even regresses all by itself.

In order to prevent actinic keratosis, it makes sense to apply an intensive light protection. This does not only include sun creams but also the wearing of appropriate clothing and the avoidance of the particularly light-intensive midday sun. Protection should already be started in childhood. This is because sunburns from childhood and adolescence in particular increase the probability of developing actinic keratosis enormously.

Men who are bald or have thinning hair should always remember to protect their heads from the sun.