Actinic Keratosis

Symptoms

• Usually asymptomatic; some lesions tender or pruritic with friction
• Sandpaper texture often felt before lesion is seen — diagnostic clue
• Patient concern about cosmetic appearance

Signs / physical exam

• Rough, scaly, erythematous papule or macule on sun-exposed skin — face, scalp (especially balding), ears, lower lip (actinic cheilitis), dorsal hands/forearms, neck, upper chest
• Typically 2-6 mm; gritty sandpaper texture
• Color: pink, red, tan, brown, or skin-colored with overlying scale
• Often multiple — 'field cancerization' background of sun-damaged skin with telangiectasias, dyspigmentation, lentigines
• Variants:
• • Hypertrophic AK — thick adherent scale (cutaneous horn variant)
• • Pigmented AK — brown discoloration, mimics solar lentigo
• • Atrophic AK — minimal scale, erythematous patch
• • Lichenoid AK — violaceous, biopsy-needed
• • Actinic cheilitis — lower lip with persistent scaling, fissuring, loss of vermilion border definition (premalignant for lip SCC)

Classic findings

Gritty sandpaper-textured pink scaly papule on a sun-damaged background of an older fair-skinned adult.

Diagnostic criteria

Clinical: characteristic rough scaly papule on sun-damaged skin of older adult; biopsy if suspicion of SCC.

Labs

• Clinical diagnosis sufficient for typical lesions
• Skin biopsy if atypical features (induration, ulceration, bleeding, rapid growth, >1 cm, tenderness, refractory to therapy) — to exclude invasive SCC
• Dermoscopy: strawberry pattern (red pseudonetwork with white halos around hair follicles) helpful, especially for pigmented AKs

Imaging

• Not indicated

First-line

• Lesion-directed therapy for isolated AKs:
• • Cryotherapy with liquid nitrogen — 5-10 seconds per lesion; most common; cure ~67-83%; possible hypopigmentation
• • Curettage ± electrodessication for hypertrophic or persistent AKs
• Field therapy for multiple AKs or field cancerization (preferred when ≥6-10 AKs in an area):
• • 5-fluorouracil 5% cream BID × 2-4 weeks (significant inflammation during therapy)
• • Imiquimod 5% cream 3-5x/week × 4-16 weeks
• • Tirbanibulin 1% ointment daily × 5 days (newer agent, shorter course, less inflammation)
• • Diclofenac 3% gel BID × 60-90 days (gentler but slower)
• • Photodynamic therapy with topical 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) + blue or red light — preferred for field treatment in many practices
• • Combination therapy: cryotherapy of individual AKs + topical field therapy
• Sun protection: broad-spectrum SPF 30+ daily, sun-protective clothing, hat, sunglasses, shade
• Surveillance: total body skin examination every 6-12 months in patients with AKs

Hypertrophic / cutaneous horn

• Biopsy at base (cutaneous horn is a clinical description — underlying lesion can be SCC, AK, or seborrheic keratosis)
• Excision or curettage with margin pathology

Actinic cheilitis

• Field therapy: 5-FU, imiquimod, or photodynamic therapy on lip vermilion
• Vermilionectomy or CO2 laser ablation for severe diffuse involvement
• Lip protection: SPF 30+ lip balm with reapplication; hat with brim

Organ transplant recipient

• Aggressive treatment of all AKs
• Acitretin 10-25 mg/day as chemoprevention (significantly reduces AK and SCC incidence)
• Nicotinamide (vitamin B3) 500 mg BID — reduces new AKs and SCC/BCC in immunocompetent (modest evidence in transplant)
• Consider switching to mTOR inhibitor (sirolimus) from calcineurin inhibitor (in coordination with transplant team)

Second-line / adjunct

• Nicotinamide 500 mg BID — proven to reduce new AK and non-melanoma skin cancer in immunocompetent high-risk patients (ONTRAC trial)
• Resurfacing procedures (chemical peel, dermabrasion, fractional laser) for diffuse field disease
• Counsel: AKs may recur after any therapy — surveillance and field maintenance are key