Actinic keratoses are common, benign skin tumors. Seborrheic keratoses, another form of benign skin tumors, are often confused with actinic keratoses. However, significant differences exist in the visual morphology, prognosis and treatment of these two skin lesions.
Seborrheic keratoses are common wart-like lesions that occur most commonly in elderly individuals. There is no known risk of a seborrheic keratosis developing into a cancerous condition. The diagnosis of an actinic keratosis, on the other hand, carries the potential of the lesion developing into an invasive skin cancer called squamous cell carcinoma.
Like seborrheic keratoses, these actinic keratotic lesions commonly develop on sun-exposed areas such as the face and hands. Actinic keratoses also occur with increasing frequency as individuals age. But unlike the seborrheic keratoses which have an undefined etiology, a lesion identified as an actinic keratosis is known to arise directly from ultraviolet (UV) light induced DNA mutations. In individuals with a history of significant sun burns or evidence of heavy sun exposure, such as telangectasias and elastosis, the potential diagnosis of actinic keratosis deserves particular consideration.
Actinic keratoses occur with higher frequency in Caucasian people, especially those with fair skin. Actinic keratoses occur more frequently in men. This is in contrast to seborrheic keratoses which occur with equal frequency in all ethnicities and equally between men and women. It is theorized that the increased frequency of actinic keratoses in men is because men are more likely to have an outdoor occupation.
The diagnosis of an actinic keratosis is determined by the growth pattern and physical characteristics. Actinic keratoses usually begin as small, rough spots that feel like sandpaper and are very difficult to see. They progress to scaly plaques with an erythmatous (reddish) base and most often appear as multiple discrete, flat or raised, keratotic lesions. An actinic keratosis can be pink, tan or gray. While a seborrheic keratosis often has plugged hair follicles, and thus less hair growth than the surrounding area, the hair follicles in an actinic keratosis are generally not involved.
Seborrheic keratoses are generally only treated if they are bothersome to the individual. Actinic keratoses, however, usually require treatment. In very elderly people, the physician may simply monitor the skin lesion for concerning changes on a regular basis. In younger individuals, particularly those with multiple lesions, the actinic keratosis is treated with a topical medicine or via cryosurgical freezing of the skin lesions.
Cohn BA: From sunlight to actinic keratosis to squamous cell carcinoma. J Am Acad Dermatol 2000 Jan; 42(1 Pt 1): 143-4