Actinic keratosis
Actinic keratosis is a precancerous, gritty, sandpaper-like scaly macule or papule on chronically sun-exposed skin that carries a 5 to 10 percent lifetime risk of progressing to squamous cell carcinoma. Isolated lesions are destroyed with cryotherapy, while numerous lesions marking a field of sun damage are treated with topical fluorouracil, imiquimod, or photodynamic therapy to clear subclinical disease and prevent skin cancer.
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What this article covers
- Overview
A precancerous epidermal lesion of chronically sun-damaged skin, actinic keratosis is the pivot point between benign sun damage and squamous cell carcinoma (SCC).
- Epidemiology
Occurs on chronically sun-exposed sites, face, scalp, ears, and dorsal hands, in proportion to cumulative lifetime ultraviolet exposure.
- Risk factors
Cumulative ultraviolet (sun) exposure, the dominant driver of actinic keratosis and of the field of subclinical damage surrounding each visible lesion.
- Pathophysiology
Chronic ultraviolet exposure damages epidermal keratinocytes, producing the dysplastic, hyperkeratotic epidermal change that defines the lesion.
- Clinical features
Gritty, sandpaper-like texture on palpation is the most distinctive finding, often more apparent to touch than to sight.
- Differential diagnosis
Squamous cell carcinoma (invasive): a firm, indurated, adherent-scale nodule or plaque that may ulcerate, bleed, or crust, unlike the flat, non-indurated macule or papule of actinic keratosis.
- Diagnosis
This is a clinical diagnosis established by inspection and palpation: the gritty, sandpaper texture on sun-exposed skin in a fair-skinned patient is diagnostic.
- Management
First, determine whether disease is isolated or field/multiple, since this decision sets the entire treatment pathway; treatment of actinic keratosis is undertaken to prevent squamous cell carcinoma, not for cosmesis alone.
- Complications
Progression to invasive squamous cell carcinoma, occurring in an estimated 5% to 10% of untreated actinic keratoses over a patient's lifetime, the principal reason every lesion is treated.
- Prognosis
Most actinic keratoses respond to lesion-directed or field therapy, with visible clearance expected over the treatment course, days for cryotherapy, weeks for topical field agents.
- Prevention
Sun protection on chronically exposed sites (face, scalp, ears, dorsal hands) to limit the cumulative ultraviolet exposure that drives new lesion formation.
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- Basal cell carcinoma
Basal cell carcinoma is the most common skin cancer, arising from the basal layer of the epidermis after ultraviolet-driven mutation of the PTCH tumor-suppressor gene, and it rarely metastasizes but can cause significant local tissue destruction if untreated. Diagnosis is confirmed by shave or punch biopsy, and treatment is chosen by risk: standard excision or Mohs micrographic surgery for higher-risk tumors, with curettage and electrodesiccation or topical imiquimod or fluorouracil reserved for low-risk superficial or nodular disease.
- Seborrheic keratosis
Seborrheic keratosis is an extremely common benign epidermal growth of older adults that presents as a round or oval, sharply demarcated, waxy or verrucous plaque with a classic stuck-on appearance on the face, trunk, or upper extremities. Diagnosis is clinical based on the stuck-on morphology; no treatment is required, and irritated or cosmetically bothersome lesions can be removed by cryotherapy, curettage, or shave removal.
- Sunburn
Sunburn is a self-limited, acute inflammatory reaction of the skin to excessive ultraviolet radiation, mainly UVB, producing erythema, tenderness, and sometimes blistering that is confined to the epidermis. Diagnosis is clinical from the sun-exposure history and pattern of redness, and first-line treatment is UV avoidance with cool compresses, a bland moisturizer, and oral ibuprofen 200 mg every 4 to 6 hours for pain, with topical hydrocortisone 1% for itch.