Actinic keratosis – dangerous signs of the sun

The cumbersome term “actinic keratosis” hides an early stage of light skin cancer, the development of which, in many cases, can be traced back to UV radiation. Rough, scaly skin changes form, particularly on sun-exposed skin areas.

Early treatment of actinic keratosis is essential to prevent the development of an advanced skin tumour. Various surgical, physical and chemical treatment methods can be used. In any case, consistent UV protection is essential for treating actinic keratosis.

What does actinic keratosis mean?

Actinic keratosis (Greek “aktis” for ray) means “keratinization disorder caused by radiation”. The terms light keratosis and solar keratosis are used synonymously.

Actinic keratosis should not be confused with the term “seborrheic keratosis” (senile wart), which describes a benign and harmless skin tumour.

 

Definition: What is actinic keratosis?

Actinic keratosis is the initial stage of white skin cancer ( squamous cell carcinoma, spinalioma), which is limited to the epidermis (carcinoma in situ) and, unlike advanced (invasive) squamous cell carcinoma, does not penetrate the deeper layers of the skin.

Therefore, the term “actinic precancer”, which is also common, is not entirely clear. According to the definition, precancerous skin changes have an increased risk of degeneration and are, therefore, only a precursor to cancer.

Risk Factors: Who Gets Actinic Keratosis?

The main risk factor for developing actinic keratosis is chronic skin photodamage due to frequent and intensive exposure to the sun. The number of sunburns is less significant than the cumulative UV radiation. Thus, the risk of actinic keratosis increases with age.

Men with light skin are particularly affected. Other risk factors are chronic immunosuppression – for example, after an organ transplant – and infection with specific human papillomaviruses (HPV).

 

Appearance and Symptoms: How to Recognize Actinic Keratosis?

Typically, actinic keratosis presents as rough, scaly patches or flat plaques about five millimetres to one centimetre in diameter that may merge into a flat lesion. The colour can vary from skin colour to reddish to yellow-brown.

Other symptoms, such as itching, burning, and pain, occasionally occur when touched. Affected skin areas are “sun terraces” such as the nose, forehead, cheeks, auricles, hairless scalp and arms. On the lip, the condition is called actinic cheilitis.

Histology confirms diagnosis

If actinic keratosis is suspected, the whole body is usually examined using a reflected-light microscope for skin changes. Actinic keratosis can be divided into three degrees of severity (according to Olsen):

• Grade 1 (mild): Individual reddish patches, millimetre in size, more palpable than visible
• Grade 2 (advanced): whitish keratinized and raised plaques, clearly palpable and visible
• Grade 3 (severe): thick, warty skin growths

Five subgroups of actinic keratosis

In unclear cases, a tissue sample (biopsy) should be taken to rule out an advanced spinalioma. Based on histology (microscopic tissue structure), five different subgroups of actinic keratosis can be distinguished:

• hypertrophic actinic keratosis
• atrophic actinic keratosis
• bowenoid actinic keratosis
• acantholytic actinic keratosis
• pigmented actinic keratosis

 

How is actinic keratosis treated?

There are numerous treatment methods for actinic keratosis. The treatment decision should be made individually for each patient and depends on various factors such as the number and size of the affected skin areas, previous illnesses, and the patient’s wishes and ideas.

The international guideline recommends classifying patients into four subgroups for the treatment of actinic keratosis:

1. Patients with a maximum of five definable skin lesions in one body region
2. Patients with at least six definable skin changes in one body region (multiple actinic keratoses)
3. Patients with at least six skin lesions in one body region and one contiguous skin area with chronic UV damage and keratinization (field cancerization)
4. Patients with additional immunodeficiency (immunosuppression due to medication or disease)

Treatment methods in actinic keratosis

The following is overview of the various therapy options and their advantages and disadvantages. However, not all treatment methods for actinic keratosis are covered by health insurance, so it is best to ask your health insurance company which costs are covered.

• Operation
• Require
• laser treatment
• photodynamic therapy
• chemical treatment

Surgery for individual skin changes

If only individual skin areas are affected by actinic keratosis, these can be removed with a scalpel (shave excision) or a sharp spoon (curettage).

The removed tissue is then examined histologically – this treatment method excludes invasive squamous cell carcinoma.

Disadvantages are the usual risks of an operation, such as wound infection and scarring.

 

Freezing: treatment with nitrogen

Freezing with liquid nitrogen (cryotherapy) is an effective alternative to the surgical treatment of single actinic keratoses. Local anaesthesia is not necessary, but the procedure can be painful.

Possible side effects include skin irritation up to the formation of blisters and permanent light discolouration of the treated skin area since freezing can also destroy pigment-forming cells.

In addition, no histological examination is possible – therefore, the treatment is unsuitable if there is a suspicion of an invasive skin tumour.

Risk of infection with laser treatment

Laser treatment is suitable for the removal of both single and multiple actinic keratoses and for patients with field cancerization.

The advantage is that the skin can be removed over a large area, so early skin changes that are not yet visible can also be detected (field-directed therapy). However, a histological examination is not possible.

However, laser therapy can also be painful and carries the risk of scarring and discolouration of the skin.

 In addition, the risk of infection is increased due to the large wound area, which is why laser therapy is not recommended for patients with a weakened immune system.

Photodynamic therapy for multiple actinic keratoses

In photodynamic therapy, the affected skin areas are pretreated with 5-aminolevulinic acid or methyl 5-amino-4-oxopentanoate as an ointment or patch. The tumour cells absorb the active ingredients much more than normal skin cells, increasing sensitivity to light with a specific wavelength.

After an exposure time of around four hours, the skin is irradiated with a particular light source, which destroys the affected tissue. Pain, burning, and skin irritation can occur.

The treatment is particularly suitable for extensively affected skin. The risk of recurrence and the risk of skin discolouration are said to be lower than with other therapies.

 

Chemical treatment with ointments and solutions

In addition to the treatment methods described, numerous chemical agents in various forms exist for the local treatment of actinic keratosis.

The patients at home can usually use the preparations, but the treatment usually lasts a few weeks to several months. We have put together an overview of the most essential active ingredients for you:

• Diclofenac in hyaluronic acid gel (Solaraze®): Diclofenac inhibits cancer cell proliferation and is particularly suitable for the face due to the few side effects. However, the treatment lasts at least two to three months.
• 5-Fluorouracil: The active ingredient is one of the cytostatics and inhibits cell division. The treatment is several weeks, during which severe skin irritation can sometimes occur. Individual actinic keratoses can alternatively be treated with lower-dose 5-fluorouracil in combination with salicylic acid, which can reduce side effects.
• Ingenol mebutate: The herbal active ingredient is obtained from the Euphorbia spurge and is suitable for treating smaller skin areas. One advantage is the short duration of use, which is two to three consecutive days. The frequently occurring inflammatory reaction of the treated skin usually subsides within two to four weeks without leaving any scars.
• Imiquimod (Aldara®, Zyclara®): Imiquimod is an immune modulator for treating basal cell carcinoma ( basal cell carcinoma ) and genital warts. The active ingredient stimulates the treated skin area’s immune system, leading to an inflammatory reaction that can destroy the tumour cells.

Prognosis: how dangerous is actinic keratosis?

Actinic keratosis differs from the advanced form of cancer in that it does not penetrate the deeper layers of the skin and, therefore, cannot spread (metastasize).

The risk of developing an advanced spinalioma within ten years is about ten per cent in the case of multiple actinic keratoses and up to 20 per cent in the case of field cancerization.

Prevention through sun protection

The recurrence rate after treatment is given as ten to 50 per cent, depending on the type of therapy. However, consistent sun protection can significantly reduce the risk of recurrence and the development of new actinic keratoses.

Patients with actinic keratosis should avoid the midday sun and pay more attention to adequate sun protection. When staying in the sun, clothing with UV protection, sunglasses, a hat and sunscreen with a sun protection factor of 30 or higher are recommended.