A 44-year-old woman without disease antecedents of interest was referred with an erosive lesion on the left cheek mucosa, of whitish margins (Fig. 1), that had been present for the previous 8 months and caused discomfort. She also had skin lesions, with erasure of the lip line (Fig. 2, Fig. 3). Laboratory tests were requested, together with a buccal mucosa biopsy. Biopsy photomicrograms can be accessed here (Fig. 4, Fig. 5, Fig. 6, Fig. 7).