solar keratosis
Meaning of solar keratosis: A sun-damage lesion easier to feel than to see, and the visible tip of a much wider field of altered skin.
Definition of solar keratosis
Solar keratosis is a rough, scaly patch that develops on skin after years of sun exposure, most often on the face, scalp, ears, forearms and backs of the hands. The patches are small, dry and sandpapery, sometimes pink or brown, and are frequently found by touch before they are noticed by eye. A minority go on to become squamous cell skin cancer.
Is it cancer or not?
It sits on the boundary, and specialists disagree about where the line falls. The cells in the patch carry the genetic damage of a cancer and are abnormal throughout the outer layer of skin, but they have not broken through the base into the tissue below, so they cannot spread. Some pathologists call the lesion precancerous; others call it the earliest form of squamous cell carcinoma, confined to the surface. The practical difference is small, since either way the patch is treated as something that might progress. Any single patch is far more likely to stay as it is, or to fade, than to turn invasive, yet someone carrying many of them has a real chance that one eventually will.
What is field damage?
The patch is not an isolated fault. Ultraviolet light striking an area of skin over decades mutates cells across the whole exposed surface, and the visible scaly spots are simply where the damage crossed a threshold. The skin between them looks weathered but otherwise normal, and already carries the same mutations. This is why treatment is often aimed at a whole region rather than at individual spots, why fresh patches keep appearing after old ones clear, and why a bald scalp or a forearm collects them in numbers. It also explains why the skin surrounding a lesion gets examined rather than only the spot a person points to.
What else looks like it?
| Lesion | How it differs |
|---|---|
| Solar keratosis | Gritty and rough, flat or barely raised, on sun-exposed skin |
| Seborrheic keratosis | Waxy and stuck-on in appearance, harmless, unrelated to sun |
| Squamous cell carcinoma | Thicker and firm, may be tender, may ulcerate or bleed |
| Basal cell carcinoma | Pearly rim with fine vessels, often eroded at the center |
The naming has drifted over time. Actinic keratosis, built on a word meaning ray, is the term used in dermatology and in pathology reports and means exactly the same thing. The older label senile keratosis blamed age instead of sunlight and has fallen out of use, because the cause is accumulated ultraviolet exposure rather than the passing of years. The cancers these patches can turn into belong to the group called nonmelanoma skin cancer, far more common than melanoma and far less often deadly.
Also known as
Used in a sentence
Solar keratosis was noted on the scalp and on the backs of both hands.
Good to know
These patches indicate that a whole sun-exposed area carries ultraviolet damage rather than one isolated fault, so new lesions commonly appear beside treated ones, and the older name senile keratosis wrongly credits age rather than sunlight.
Word origin
Where “solar keratosis” comes from
Solar comes from the Latin sol, meaning sun. Keratosis joins the Greek keras, meaning horn, to the ending -osis marking a condition, and points to a build-up of the tough protein that also forms hair and nails.