This article was last reviewed and updated on August 8, 2019
by Allison Osmond, MD FRCPC
Actinic keratosis is a non-cancerous skin disease.
It is a very common condition caused by long term exposure to the sun.
There are different types of actinic keratosis and some types are considered a pre-cancerous condition because they can turn into a type of cancer called squamous cell carcinoma.
The surface of the skin is called the epidermis. The cells that make up the epidermis include: keratinocytes, melanocytes, Merkel cells, and cells of the immune system. The keratinocytes in the epidermis produce a material called keratin which makes the skin waterproof and strong and protects us from toxins and injuries.
Beneath the epidermis, there are blood vessels, connective tissue, and fat (called the dermis and subcutaneous tissue). The epidermis is separated from the dermis and subcutaneous tissue by a very thin layer of tissue called the basement membrane.
What is actinic keratosis?
Actinic keratosis is a non-cancerous disease that affects the keratinocytes in the epidermis. When viewed through a microscope, the epidermis is made up of several layers of keratinocytes stacked one on top of another, like the bricks in a house. Actinic keratosis starts in the keratinocytes at the very bottom of the epidermis which are called basal cells. In actinic keratosis, the basal cells look bigger, darker, and appear more disorganized compared to the more superficial keratinocytes.
Actinic keratosis is a very common condition caused by long term exposure to the sun. Actinic keratosis commonly occurs on the face, lips, ear, back of the hands, arms and scalp. However, actinic keratosis can develop any where on the body where the skin has been exposed to the sun for long periods of time. It is not uncommon for people to have multiple areas of the skin with actinic keratoses.
When you have actinic keratosis, you or your doctor might notice an area of the skin that looks scaly or red. When similar changes affect the lips, it is called actinic cheilitis. When viewed through the microscope, actinic keratosis and actinic cheilitis look the same. Older age, fair skin, and chronic sun exposure are risk factors for developing actinic keratosis.
Types of actinic keratosis
Pathologists divide actinic keratosis in groups called variants based on how the cells look under the microscope.
Variants of actinic keratosis include:
Acantholytic - When examined under the microscope, the cells in this type of actinic keratosis look like they are separated from each other by a small empty space.
Pigmented - This type looks dark when examined under the microscope because the cells contain a pigment called melanin.
Hypertrophic - In this type of actinic keratosis, the epidermis is thicker than normal.
Bowenoid - In this type of actinic keratosis, the abnormal cells fill the entire epidermis.
Why is this important? Bowenoid actinic keratosis is very important because it is considered a pre-cancerous disease that can, over time, turn into a cancer called squamous cell carcinoma.
For this reason, Bowenoid actinic keratosis needs to be completely removed in order reduce the risk of developing cancer and to avoid recurrence.
Depending on the type of actinic keratosis your have, or if you have multiple, your doctor may treat you with a cream to apply to your skin or light therapy (in addition to your biopsy).