Bowen’s disease

### What you need to know A 68 year old woman with skin type 1 presents with an 18 month history of a well circumscribed 10 mm erythematous scaly patch over her left shin. Since retirement, she has lived in Spain for part of the year and has now returned to the UK, worried that the patch has increased in size. In Bowen’s disease the full thickness of the epidermis is dysplastic with atypical keratinocytes, but these have not yet breached the basement membrane to become a squamous cell carcinoma. Reflecting this, Bowen’s disease is also commonly known as squamous cell carcinoma in situ and as intraepidermal or intraepithelial carcinoma. Historically, progression of Bowen’s disease to squamous cell carcinoma was believed to be 3-5%.1 However, a 2017 study suggested that it may be much higher, with 16.3% of 566 cases of biopsy-proven Bowen’s disease found to have squamous cell carcinoma when treated surgically.2 This article outlines the assessment and management of Bowen’s disease in a primary care setting. Rarer variants of Bowen’s disease may present as pigmented plaques, nail dystrophy or discolouration, or patches and plaques in the genitalia, but this article focuses on the common presentation likely to be seen in primary care. ### How this article was made We conducted a literature review of articles and guidelines, reviewed dermatology textbooks, and sought expert advice from general practitioners and consultant dermatologists regarding Bowen’s disease. The classic presentation of Bowen’s disease is of an asymptomatic, well circumscribed, solitary, erythematous patch or plaque on a sun-exposed site (typically head, neck, or limb), usually 10-15 mm in diameter that has been slowly growing (fig 1 …