Bowen's disease occurs when there is a growth of cancer cells in the outer layer of the skin (epidermis). These cancer cells stay within the outer layer of the skin. Unlike most forms of cancer, these cells can't spread elsewhere. So, Bowen's disease itself is not serious. However, there is a small risk that, over time, it can develop into a more advanced form of skin cancer, which does cause problems.
This is a companion discussion topic for the original article at https://patient.info/cancer/skin-cancer-types/bowens-disease