Carcinoma in situ, Bowen’s disease, i.e. epidermal carcinoma of the skin, is a more severe skin change than actinic keratosis. Atypical prickle cells are found throughout the thickness of the epidermis. If the pathologist finds atypical prickle cell islets also in the dermis, the diagnosis is in fact squamous cell carcinoma. Epidermal cancer also responds to the more recent non-invasive treatments, e.g. photodynamic therapy and the application of imiquimod cream.