Differentials
Actinic keratosis
SIGNS / SYMPTOMS
Appears as red scaly papules or plaques that may be pruritic or tender.
The extent of hyperkeratosis varies, and retention of compact keratin layers may result in the formation of a cutaneous horn.
INVESTIGATIONS
Biopsy will show basal layer keratinocyte atypia that does not involve the full thickness of the epidermis.
Basal cell carcinoma
SIGNS / SYMPTOMS
Presents as pearly papules or plaques with rolled borders, telangiectasias, and ulceration when tumours become larger.
INVESTIGATIONS
Biopsy shows tumour nests with basaloid differentiation with large nuclei and scant cytoplasm. Significant keratinocyte atypia or mitotic figures are not found.
Seborrhoeic keratosis
SIGNS / SYMPTOMS
Tends to appear 'stuck on' with a waxy or scaly appearance with varying degrees of pigmentation.
INVESTIGATIONS
Biopsy shows proliferation of keratinocytes without atypia, often with pseudohorn cysts.
Common warts
SIGNS / SYMPTOMS
Red and/or black dots may be visible upon paring, representing tips of superficial dermal capillaries.
INVESTIGATIONS
Biopsy may show viral cytopathic changes in the superficial spinous and granular layers (or pseudoepitheliomatous hyperplasia). Keratinocyte atypia is rare.
Prurigo nodularis
SIGNS / SYMPTOMS
A 'picker's nodule' is a benign lesion caused by chronic rubbing, scratching, or picking.
INVESTIGATIONS
Biopsy shows irregular acanthosis of the epidermis and a thickened granular layer (or pseudoepitheliomatous hyperplasia). No keratinocyte atypia is present.
Amelanotic melanoma
SIGNS / SYMPTOMS
A lesion that has little or no colour or may appear red, pink, or scar-like white.
It has an asymmetrical shape and an irregular, faintly pigmented border.
Always considered in a differential of a changing or growing neoplasm.
INVESTIGATIONS
Biopsy shows a melanocytic neoplasm.
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