Intriguingly, although the inhibitors are administered systemically, keratoacanthomas and SCC in situ develop in patients treated with Raf inhibitors (Brower, 2010; Cichowski and Janne, 2010; Wimmer and Baccarini, 2010), underscoring the connection between Raf-1 activation and epidermal proliferation and tumourigenesis. Here, RAF1 is linked to keratoacanthoma.