Bowen's Disease

Bowen's disease is squamous cell carcinoma in situ of the skin that was first described by John Bowen in 1912. In the past is has been thought of as indicative of underlying malignancy but more recent surveys of better methodology have suggested that it is not a paraneoplastic disease.^1,2

The incidence in the UK is around 14 per 100,000 per year but a study of white people from Hawaii gave 10 times that figure, presumably because of exposure to strong sunlight.³ When associated with sunlight the risk is much higher in white races. Some sources state that there is no difference in incidence between the sexes whilst others state that it is 3 times as common in women as in men. It tends to appear between the ages of 60 and 70.

• Exposure to sunlight, especially with fair skin, is a strong risk factor.
• Exposure to inorganic arsenic is less important than it was.
• Virus infection has been implicated, particularly human papillomavirus (usually HPV 16 but more rarely HPV 2).
• Other chemical carcinogens and trauma have been suggested but often no specific risk factor is found.
• Arsenic used to be found in Fowler's solution used to treat psoriasis, Gay's solution used to treat asthma, contaminated well water and some pesticides.
• More travel to exotic locations and a shrinking ozone layer make it an increasing problem.
• Suppression of the immune system appears to be a risk. Malignant and premalignant skin tumours are more common in patients who have received organ transplants. The risk is higher for heart recipients than kidney recipients, perhaps as they are more strongly immunosuppressed.⁴ The literature also contains a number of reports of Bowen's disease, quite often extensive, in patients with HIV infection.

• It presents as a slowly growing erythematous, patch or plaque. It is sharply demarcated, scaling or hyperkeratotic, with a pink or red surface. There may be a small erosion or it may be crusted.
• Lesions are usually asymptomatic but can bleed. It may be a solitary or multiple lesions. Two thirds are solitary.
• They are often found on sites exposed to sun and are commonest on the head and neck followed by the limbs but they may occur elsewhere, for example as a disorder of the vulva. When it arises on the glans penis, it is referred to as erythroplasia of Queyrat. They vary in size from a few millimetres to a few centimetres. They are rarely pigmented. Diagnosis is often delayed as it is asymptomatic and may appear similar to benign skin lesions.

A characteristic feature is that it is well demarcated.

• Discoid eczema , other forms of eczema ,
• Psoriasis
• Lichen planus
• Seborrhoeic (solar) keratosis
• Superficial basal cell carcinoma
• Malignant melanoma
• Mammary Paget's disease

A shave or punch biopsy is required for histological diagnosis. Where possible include a hair follicle in the biopsy.

• Surgical excision is usually satisfactory for small lesions not on the face or digits. Although the lesion looks clearly demarcated it may extend beyond the apparent boundary and so at least 5mm of clearance should be allowed.
• Mohs micrographic surgery⁵ is excellent for larger lesion and those on the face or digits where it is important to be as sparing as possible with the extent of excision.
• Cautery, curettage and cryotherapy may be satisfactory but they give no histological diagnosis and may fail to reach all the affected tissue.
• Superficial x-ray treatment may be best for those unsuitable for surgery, especially with multiple lesions.
• Topical 5 fluouracil cream may be used. It may be preceded by keratolytic or cryotherapy. It can be used under occlusion or with iontophoresis where an electrical current drives it into the tissues.⁶
• Photodynamic therapy (PDT) may be valuable.⁷ It is gaining wider acceptance and appears better for patients who developed the disease whilst immunosuppressed for transplantation.⁸ It may be used for a number of other skin conditions too.⁹ It can be rather painful and some form of topical anaesthesia is often required.¹⁰
• Imiquimod 5% cream appears to be an effective treatment for Bowen's disease on the lower limbs.¹¹

This is excellent, especially with treatment. Untreated, 3 to 5% progress to invasive squamous cell carcinoma but metastases are rare.