Actinic Keratoses
What are AKs? Actinic keratoses are potentially precancerous
thickenings of the epidermis, the outer-most layer of the skin. The word
keratosis comes from the Greek "kerat-", which means "horn", or scale, and the
suffix "-osis", meaning "condition". The word actinic is derived from the Greek
word "aktis", meaning "ray". AKs most often arise on skin that has been exposed
to a lot of ultraviolet (UV) radiation over time, either rays of sunlight or
artificial UV light such as tanning booths or phototherapy. There may be many
years, or decades, between the time of significant UV exposure and the
development of AKs. AKs are most commonly seen in people with fair skin types,
since those individuals are most susceptible to UV-induced skin damage. AKs are
also common in immunosuppressed individuals, such as people who have had a solid
organ transplant. Although actinic keratoses are technically not cancerous, a
small percentage of them can become cancerous over time, evolving into a type of
non-melanoma skin cancer called squamous cell carcinoma (SCC). It is not
possible to know at their onset which AKs will become cancers and which ones
won't, hence it is generally advised that they be removed to prevent their
progression to SCC.
What do AKs look like? AKs may appear as pink, skin-colored, or gray,
flat, scaly growths that have a rough, "sandpapery" feel when touched. AKs vary
in size but are often about the diameter of a pencil eraser and range in
thickness from barely elevated above the skin surface to a thick "warty" growth.
Sometimes they will disappear on their own over time, as a result of the
patient's immune system recognizing and destroying them, but they often persist
for many months or years. Many AKs have no symptoms, especially if they are
small and thin, but sometimes they feel tender or itchy, especially after
exposure to UV light.
What does an AK look like if it is changing into a skin cancer? AKs that
are becoming cancerous often do so fairly rapidly, over a period of
approximately three weeks. They may enlarge in diameter and thickness, become
inflamed (red, swollen, sore), and have very thick scale on top or a central
crater.
How are AKs treated? There are many treatment options for AKs. AK
treatments can be divided into several broad categories: destructions,
chemotherapy, and photodynamic therapy. Destructions are procedures designed to
physically remove the AKs by cutting, scraping, chemical peels, lasering,
cauterizing ("burning"), or freezing. One of the most common methods of AK
destruction is cryotherapy, or freezing with liquid nitrogen. The intense cold
of the liquid nitrogen instantly freezes the targeted skin cells so they die,
scab, and peel off. Topical chemotherapy is drugs applied to the skin to remove
AKs. Drugs used in this way include 5-fluorouracil cream (Efudex or Carac),
diclofenac sodium gel (Solaraze), and imiquimod cream (Aldara). Photodynamic
therapy (Blu-U) involves applying a chemical to the AKs and then exposing them
to a special light that activates the chemical. This leads to a chemical
reaction that irritates and subsequently destroys the AKs. If an AK looks
suspicious for having possibly become cancerous, a biopsy (sampling) of the AK
will be performed so that it can be examined microscopically.
Which AK treatment option is best? There is no one best treatment for all
AKs. Which treatment is ultimately selected will vary depending on how many AKs
there are, how thick they are, what body areas are affected, and other
circumstances such as the patient's general health and ability to participate in
the treatment. Your dermatology health care provider can review the pros and
cons of each treatment with you and help you decide which treatment is most
appropriate for each particular situation.
How can AKs be prevented? AKs can be prevented by protecting the skin from
excessive amounts of UV exposure. A combination approach to sun protection is
most effective. Avoid prolonged time in the sun during the middle of the day
(10am – 4pm), when the sun's rays are most intense. Seek shade when possible.
Wear protective clothing to shield the skin, including hats and sunglasses.
Apply sunscreen with at least SPF 15 twenty minutes before exposing skin to UV
light, and reapply it every ninety minutes if you get wet, perspire a lot, or
wipe off the skin. It takes one ounce of sunscreen to cover an average-sized
adult from head to toe. Remember that UV light passes through clouds and window
glass, so don't ignore sun protection on cloudy days or when traveling in
vehicles. If patients have already started to grow AKs, it is likely that they
will continue to do so, even if they are very careful about sun protection on an
ongoing basis in the future. However, it is still important that they continue
to practice careful sun protection measures. People cannot go back in time and
undo the UV damage that has already occurred to their skin, but they can help
prevent additional damage, which in turn may reduce the number of AKs they
develop later and their risk of future skin cancers.
Elizabeth S. Miller, M.D., FAAD, FAAP