- In situ, intraepidermal squamous cell carcinoma.
- Associated with sun exposure, radiotherapy, carcinogens, immunosuppression and HPV-16.
- Small risk of progression to invasive cancer. Many have had or will develop basal cell carcinoma.
- More common in women and those over 60 years. The lower leg is a common site.
- Presents with slow growing, scaly erythematous plaque with irregular borders. Usually a single lesion but can be multiple.
- Diagnosis confirmed by biopsy.
- Treatment depends on lesion age, site, size and thickness.
- 5-fluorouracil has a good cure record.
- Topical imiquimod, which has both anti-HPV and anti-tumour effects.
- Cryotherapy can be used but may cause ulceration. The failure rate is 5-10 per cent.
- Photodynamic therapy is particularly useful for patients with multiple lesions.
- Excision leads to low recurrence, but site of lesion may be a contraindication.
- An eczematous response to an allergen or external irritant agent.
- Common allergens are nickel, chromate topical antibiotics, perfumes, rubber accelerators and preservative chemicals.
- Irritants include detergents, soaps, acids, alkalis, powders, dust or low humidity. T-cell mediated immune response is not involved.
- Photo-induced allergic or toxic reactions can cause eczematous reaction.
- Accounts for 4-7 per cent of dermatological consultations.
- Presents with itchy erythema, vesiculation, dryness, lichenification and fissures.
- Area may be well demarcated and limited to contact area.
- Risk of secondary infection.
- Patch testing for persistent, unresponsive eczema where allergy a possibility.
- Avoidance of irritant or allergenic substances.
- Protect hands with cotton lined or polyvinyl gloves.
- Frequent use of emollients and soap substitutes.
- Topical steroid ointments.
- Other available treatments for steroid-resistant problems are tacrolimus, psoralen and UVA light treatment, azathioprine and ciclosporin.