A 36-year-old woman complains of dryness and peeling of her lower lip vermillion border. Both dryness and peeling have been observed for a month. Application of indifferent ointments was ineffective. Objectively the vermillion border of the lower lip is bright red, moderately infiltrated, and densely covered in white-gray scales, that cannot be removed without pain and bleeding. The lesion focus contains concave areas, while on the periphery there are patches of dull epithelium that look like irregular white stripes. What is the most likely diagnosis?