Actinic keratosis

Key points:

• estimated around 10% of them becomes Squamous cell carcinoma 
• thought to be an intraepidermal lesion 
• multiple treatment modalities, the most common one is cryotherapy
• biopsy lesion if it does not respond to treatment

What is actinic keratosis?

• They are keratotic lesions with malignant potential 
• They are considered intraepidermal, pre-cursor or early lesions of squamous cell carcinoma 
• lesions are most commonly found in the sun-exposed areas of elderly patients with fair skin types who have had significant sun exposure in their lifetime

What are the histological changes?

• epidermal cell dysplasia 
• dilated upper dermal blood vessels 
• degeneration of collagen and elastin in the dermis (solar elastosis)

Who's at risk?

• Celtic descents 
• Skin types 1 and 2 
• immunosuppressant therapy
• elderly

What are the differential diagnoses?

• BCCs
• lupus erythematous
• actinic porokeratosis
• SCCs

How does it present?

• usually in caucasians > 40 in sun exposed area
• actinic keratoses initially present as a poorly defined area of redness or telangiectasia
• over time, the lesion becomes more defined and develops a thin, adherent, yellowish or transparent scale
• with time, the adherent scale becomes progressively thicker and yellow in colour 

How is it diagnosed?

• most of the time by clinical examination 
• advance lesions may require biopsies to differentiate from squamous cell carcinoma
• the histologic hallmark is a disordered epidermis with intraepidermal keratinocyte atypia 

What is the prognosis?

• small number of actinic keratoses will progress to SCC, and the trouble is we don't know which one is going to progress and which one is not 
• We think the thicker ones are more worrisome 
• SCC that develop on the ear, the scalp, or at the vermilion border are more likely to metastasise, so actinic keratoses in the above areas need to be treated aggressively

What treatment is available ?

• cryotherapy
• imiquimod
• Efudix 
• photodynamic therapy
• emollients containing keratolytics e.g. 2-4% salicylic acid in sorbolene cream
• Tretinoin 
• Laser

Why are there so many treatments available?

• None work 100 % 

Why do lesions recur after treatment?

1. The lesion may have been treated inadequately
2. Wrong diagnosis: could be BCCs, SCCs, Bowen's lupus erythematous or psoriasis. Therefore, failed treatment usually means biopsy

Reference:

• Habif: skin disease diagnosis and treatment third edition