actinic keratosis
Meaning of actinic keratosis: Often easier to feel than to see, these sandpaper patches mark skin that has absorbed decades of ultraviolet damage.
Definition of actinic keratosis
An actinic keratosis is a rough, scaly patch that forms on skin repeatedly exposed to sunlight, most often the face, scalp, ears, forearms and backs of the hands. It results from cumulative ultraviolet damage to skin cells and is regarded as a precancerous change, because a proportion of untreated lesions go on to become squamous cell carcinoma.
What does one look and feel like?
A typical lesion is small, flat or slightly raised, and dry to the touch, with a texture often compared to fine sandpaper. The color ranges from skin-toned to pink, red or light brown, and the scale may lift and return. Many are easier to find with a fingertip than with the eye, which is why they are frequently noticed during shaving or washing rather than in a mirror. They appear on skin with other signs of long sun exposure, such as mottled pigment, fine wrinkling and broken surface vessels. On the lip, the same process produces a persistently dry, cracked border rather than a discrete patch.
How likely is one to become cancer?
The chance that any single patch turns into a cancer over a given year is small, and a fair number resolve on their own. The concern is not the individual lesion but the pattern. People who develop one usually develop many, over many years, across a wide area of sun-damaged skin in which the same genetic changes are already present. That situation is described as field damage, and it explains why treatment is often aimed at a whole region rather than at one spot. Progression, when it happens, is to skin cancer of the squamous cell type, which arises from the same surface cells. Basal cell carcinoma develops from a different cell population and is not preceded by actinic keratosis.
What else looks similar?
| Growth | Usual appearance | Relation to sun and cancer |
|---|---|---|
| Actinic keratosis | Flat, gritty, scaly, poorly defined edge | Caused by ultraviolet damage; precancerous |
| Seborrheic keratosis | Waxy, warty, sharply edged, looks stuck on the surface | Unrelated to sun exposure; benign |
| Basal cell carcinoma | Pearly bump with fine vessels, sometimes crusted or ulcerated | Sun related; already a cancer |
A patch that thickens, becomes tender, bleeds or fails to settle is generally sampled rather than watched, because those changes are the ones that separate a keratosis from an invasive tumor.
Used in a sentence
Several rough, scaly patches on the scalp were identified as actinic keratosis on examination.
Good to know
Actinic keratosis is distinct from seborrheic keratosis, a common and entirely benign skin growth that shares a similar name but no connection to sun exposure or cancer risk.
Word origin
Where “actinic keratosis” comes from
Formed from actinic, from Greek aktis, meaning ray, referring to the sun's rays, and keratosis, from keras, meaning horn, and -osis, meaning a condition, describing the thickened, horn-like texture of the skin.