A 67-year-old patient complains of recurrent erosion on the red border of the lower lip. Objectively: the erosion is oval in shape, 0,8х1,3 sm in size, covered in thin scabs that reveal glossy surface with punctate bleeding when removed. There are atrophic areas of the red border detected. Infiltration elements are absent. The submandibular lymph nodes are not enlarged. What diagnosis can be assumed?