Actinic keratosis is a UV light–induced lesion of the skin, which is considered as potentially pre-cancerous. The lesion may appear on any sun-exposed area.
The disease is related to the following processes: Radiation and has an incidence of about 3 / 100.000.
Actinic keratosis, also known solar keratosis or senile keratosis due to its association with old age, is one of the most common pre-malignant lesions of skin. The condition is associated with chronic exposure to sunlight. The ultraviolet radiations in sunlight induce these scaly growths and if left untreated, they can progress into squamous cell carcinoma, although there have been reports of regression or stability of these lesions.
Excessive exposure to UV radiation, even from indoor sources like lamps etc. can trigger the development of these lesions. Excessive exposure to X-rays or industrial chemicals can also be the reason. A large number of cases of actinic keratosis have been related with the mutations in TP53 gene, the tumor suppressor gene.
Actinic keratosis has been further classified into:
The highest prevalence is in countries like South Africa and Australia where sunlight exposure and fair skinned population are relatively higher. In the northern hemisphere, it is found in 11 to 25% of the people at the age of 40 and above.
Fair skinned people are mostly commonly affected by the sunlight. Freckled individuals are at a higher risk too. Population living in areas with long-term sunlight exposure like Australia is, therefore, at higher risk of developing the disease as compared to those with low exposure to sunlight.
Older population is implicated with a high risk of actinic keratosis as damage caused by sunlight builds up over the years, hence called senile keratosis. Men are affected more than women owing to the fact that they spend relatively more time outdoors as compared to women. Caucasians are most susceptible as compared to Hispanics and Asians with darker skins.
Individuals with immunosuppression, like those undergoing cancer chemotherapy or organ transplantation, or those with immunocompromised states like diabetes or HIV are at a relatively higher risk for developing the disease. Individuals with skin disorders like xerdoderma pigmentosum and albinism are prone to develop actinic keratosis too.
The mutations in the suppressor gene cause disinhibition of tumor suppression, thereby inducing tumorigenesis. The basal cell layer of the skin is the first to get affected; it shows hyperplasia of basal cells. Pleomorphic keratinocytes start accumulating in the stratum basalis. Uninhibited growth ensues, sometimes extending into the superficial as well as the deeper layers of skin. The cellular architecture is lost as a result of rapid proliferation of cell. The nuclear-cytoplasmic ratio is high and mitotic figures are seen; a sign of malignancy.
A dense infiltration of inflammatory cells occurs. Hyperkeratosis, with occasional areas of parakeratosis is seen. Granular layer is lost. As the disease progresses, it can invade the surrounding areas, giving rise to squamous cell carcinoma. Therefore, actinic keratosis is considered a precancerous state.
In about 10% of the people, actinic keratosis progresses to squamous cell carcinoma. Early treatment prevents the development of carcinoma . Although metastasis is rare, the lesions have a high tendency for malignancy. 2 to 10% of the malignant cases can invade the internal organs, proving to be life threatening. The earlier the diagnosis; more are the chances of cure.
Actinic keratosis has been known to show signs of Bowen disease or carcinoma in situ. The patients present with the following clinical features .
Not much investigation is needed to diagnose a patient suffering from actinic keratosis. Thorough skin examination is usually enough to recognize actinic keratosis clinically. In some patients, skin biopsy is useful in ruling out the suspicion of malignancy.
Conservative treatment can be done with the following:
The surgical techniques that can be employed include the following:
Combination therapy with 5-FU followed by cryotherapy with liquid nitrogen is an effective mode of treatment.
The following measures are effective in preventing the development of actinic keratosis.
Actinic keratosis is a skin disorder that can turn into skin cancer, if not immediately tended to. The main reason is long term exposure to sunlight. Fair skinned people who spend long hours in the sun are especially at risk.
It shows up as small red skin eruptions. The skin becomes itchy and painful. The eruptions on the skin may harden and can also bleed. Avoiding sunlight as much as possible and using sunscreen lotions is the best possible preventive measure.