Partial thickness dysplasia of epidermal keratinocytes
A small minority (<1%) of actinic keratoses undergo malignant transformation into squamous cell carcinoma
Clinical presentation
Appear as scaly, erythematous papules or patches and feel gritty and rough
Occur on sun exposed skin especially scalp, face, hands - marker of chronic sun damage
Management
Lesion-based treatments - cryotherapy, curettage and cautery
Field based treatments (aimed at clearing visible and subclinical lesions over a larger area) - topical 5-fluorouracil, imiquimod, photodynamic therapy
Bowen’s disease (intraepithelial carcinoma)
Squamous cell carcinoma in situ - full thickness dysplasia of epidermal keratinocytes
Clinical presentation
Typically affects the lower legs in fair-skinned women or the torso in men
Lesions appear as slowly enlarging, well-demarkated, scaly red patch/plaque with an irregular border
A variant of Bowen’s disease can affect the genital mucosa - vulval, penile or anal intraepithelial neoplasia
Strong link with HPV-16 and 18 infection, also more common in immunosuppressed individuals (including HIV)
Management
Similar to actinic keratosis - cryotherapy, 5-flurouracil cream, imiquimod, photodynamic therapy
Keratoacanthoma
Rapidly growing epidermal tumours
Clinical presentation
Develop as a red papule with a central crater-like, crusty keratinous plug
Occur on sun-exposed skin in later life and often reach 2–3 cm in diameter
Management
Although they regress spontaneously after about 3 months, leaving a pitted scar, they are usually excised, as it can be extremely difficult to distinguish them from squamous cell carcinoma
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