Actinic keratosis, an overview of this pre-cancerous condition

By Cristiano Antonino On Apr 4, 2023

Also known as solar keratosis, actinic keratosis is counted among the pre-cancerous conditions. It is in fact a lesion due to overexposure to ultraviolet rays that can lead (in about 10% of cases) to the development of spinocellular carcinoma

The Caucasian population is predominantly affected, especially in countries with high levels of sun exposure: for those with dark skin, the risk of developing actinic keratosis is lower (as opposed to those with fair complexion, hair and eyes, who are exposed to the sun for a long time).

Men tend to suffer more, as they are less accustomed to using sunscreen.

Caused by the cumulative effect of sun exposure, the lesion is usually scaly or covered with scabs.

It appears on those areas of the body most often exposed to the sun: scalp, ears, face, lips, neck, back of the hands, forearms, shoulders.

Its treatment depends on the number of lesions, their location and the patient’s comorbidity.

Actinic keratosis: what is it?

Actinic keratosis is a skin disorder that usually appears after the age of 40 and is mainly caused by overexposure to UV radiation.

When it appears it usually presents as a small erythematous plaque of a reddish-brown colour, covered with scales or crusts.

In 26% of cases it regresses spontaneously, in other cases it progressively grows to a diameter of 2.5 centimetres or more.

Although most keratoses remain benign, in 10% of cases it can lead to spinocellular carcinoma.

However, considering the diagnoses of spinocellular carcinoma that have already occurred, 60% are the result of an untreated keratosis.

This is why it is referred to as a precancerous lesion.

Usually present in greater numbers than one, actinic keratoses are initially felt rather than noticed.

The sensation is that of touching a rough surface while, in terms of colour, one may notice a reddish (more frequently), pink or brown (more rarely) spot.

Sometimes, however, its colour is the same as that of the skin.

Risk factors, in addition to excessive and unprotected UV exposure, include fair skin (phototype I and phototype II), an immunosuppressed condition (especially in transplant patients), HPV and taking photosensitising drugs.

Actinic keratosis: symptoms

The primary symptom of actinic keratosis is the appearance of a lesion (or several lesions).

Often asymptomatic, they manifest as small erythematous scaly or crusted patches.

Rarely they may itch and give a tense sensation, sometimes they may bleed or become inflamed.

The part of the body where they most frequently appear is the face (lips, forehead, ear pinnae), followed by the arms, legs, back of the hands and scalp.

In the initial phase of the disease the person hardly perceives them by sight: much more often they notice them by touching the lesion by chance.

Recognising actinic keratosis is not always easy, not only because the lesions are initially very small but also because of the individual variety in which they appear.

This is why it is essential to make a habit of examining one’s own skin often, especially if one has a long history of sun exposure and has risk factors.

By detecting suspicious lesions in good time, you can contact your doctor who will identify the most appropriate treatment.

Other symptoms that may accompany actinic keratosis are:

erythema
papules
dry skin
plaques
itching
scaly skin
telangiectasias (pathological and visible dilatations of arterioles, capillaries and venules)

Actinic keratosis, the causes

The main cause of actinic keratosis is exposure to UV radiation.

Sun radiation accelerates skin ageing to such an extent that those with such lesions generally have skin characterised by wrinkles, freckles, sun freckles and neoplasms.

Elderly people suffer the most: most people over 80 have keratoses on their bodies.

Actinic keratosis is a cumulative disease: the more time one spends in the sun during one’s lifetime, the more radiation accumulates in the skin, the greater the likelihood that the disease will suddenly appear even if the person has not sunbathed for years.

It is not only time spent sunbathing, lying in the sun on the beach: walks in the open air and certain jobs (in agriculture as well as construction) also contribute to overexposure.

The likelihood of actinic keratoses evolving into carcinomas is higher in immunocompromised individuals such as AIDS patients, immunocompromised individuals or individuals on immunosuppressive therapy such as transplant recipients.

Actinic keratosis: diagnosis

In order to prevent actinic keratosis from developing into carcinoma, it is essential to seek medical attention at the first appearance of an abnormal lesion.

Although in the majority of cases it remains benign, its evolution into carcinoma affects approximately 10% of cases.

Typically, keratosis appears as a papule or macula of a few millimetres, with whitish or brownish-yellow scales that are difficult to peel off, and a peripheral erythematous halo.

Certain risk factors increase the risk of it giving rise to a malignant pathology:

presence of multiple, thick actinic keratoses
photodamaged skin
immunosuppressed condition
history of non-melanomatous skin tumours
painful and growing lesion

The diagnosis of actinic keratosis involves a combination of objective test, dermoscopy and skin biopsy.

During the specialist examination, the dermatologist will carefully examine the lesion to exclude pathologies that may cause similar skin signs:

lupus erythematosus (lesions are extensive, almost never scaling)
seborrhoeic keratosis (lesions are yellowish-brown and have a warty appearance)
lichen planus (papules are purplish, polygonal and itchy)
Bowen’s disease (the lesion is single and quite large, usually present on the lower limbs)
superficial basal cell carcinoma (lesions have a slightly raised pearly border)
spinocellular carcinoma (lesions grow more rapidly, are hard to the touch and often cause pain and ulceration)

In the presence of an abnormal lesion, the specialist will observe it with a dermatoscope, a small hand-held optical instrument that can magnify the lesion 10 to 20 times, illuminating it.

He will then perform a biopsy, a small skin sampling to observe the tissue under the microscope: in this way, the evolution of keratosis into carcinoma can be excluded.

Actinic keratosis: therapies and treatments

Since there is no way of predicting whether an actinic keratosis will remain benign or whether it will develop into cancer over time, treatment is aimed at eliminating it.

It is the specialist who chooses which therapy is most appropriate, based on the type of lesion, its location and the patient’s state of health.

Medical therapy

Medical therapy for the treatment of actinic keratosis consists of topical administration (i.e. in the form of a cream, to be applied directly to the lesion) of certain active ingredients

5-fluorouracil (5-FU) ointment (with concentrations varying between 0.5 and 5%) inhibits thymidylate synthase and thus prevents purines and pyrimidines from being incorporated into DNA and RNA. Widely used for the treatment of single lesions, small or large areas, it can cause irritation, erythema, burning, swelling and desquamation where it is applied;
diclofenac in 3% gel combined with hyaluronic acid, which is useful for treating large areas with multiple lesions but sometimes causes rashes;
imiquimod in cream (with concentrations varying between 3.75 and 5%) is an immunomodulator that, although fairly effective, can cause erythema, burning, itching, crusting, ulceration and pigmentation changes.

Less frequently used are ingenol mebutato cream at 0.015% (for small or infrequent lesions) and photodynamic therapy (PDT) with 5-ALA or MAL, used to treat large areas but which can only be carried out on an outpatient basis: in the latter case, light-activated photosensitising drugs are used to trigger a photochemical reaction that leads to the death of the diseased cells.

Surgical therapy

If deemed appropriate, the doctor may prefer surgical therapy to drug therapy:

surgical removal (or excision), recommended for lesions with suspected evolution into spinocellular carcinoma;
curettage (scraping), indicated for fairly large and particularly hyperkeratotic lesions. It boasts few side effects, a low probability of recurrence and sufficiently rapid healing times;
laser therapy, with CO2 laser or erbium laser, indicated for lesions in small or restricted areas such as the face or scalp. It does not cause bleeding but can result in dyschromic outcomes;
liquid nitrogen cryotherapy, suggested for single or small (no more than three) lesions. It may cause pain, swelling and the appearance of serous or serohematous blisters.

Actinic keratosis: prevention

To prevent the onset of actinic keratosis it is necessary to expose oneself to the sun intelligently:

avoid exposure during the hottest hours
always use sunscreen with SPF 15 or better still SPF 30, applying it 30 minutes before going out and then every 2 hours if you sweat a lot or go swimming
avoid sunlamps and tanning beds
use sunglasses and wide-brimmed hats
examine your skin carefully once a month
schedule a check-up at the dermatologist every year

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