Bowen’s disease looks like a red, scaly patch on the skin. It is caused by the abnormal growth of cells called keratinocytes. These are cells in the outer layer of the skin (epidermis). They don’t spread into the deeper layers of the skin. Bowen’s disease is sometimes called squamous cell carcinoma in situ. Bowen’s disease is more common in women. It usually affects people in their 60s and 70s.
If not treated, Bowen’s disease can develop into squamous cell cancer. This happens in a small number of people (about 3–5 out of every 100 who have Bowen’s disease). Squamous cell cancer is a common, curable type of skin cancer. It affects the outer layer of the skin, but can spread to deeper layers. If left untreated for a long time, squamous cell cancer can spread to other parts of the body.