A 23-year-old patient complains about a small ulcer on the red border of her lower lip that has been irresponsive to self-treatment for two weeks. Objectively: unchanged red border of lower lip has a circular ulcer of 2 mm in diameter with raised regular edges, its floor is of meatlike colour, dense, shiny, with "stearic film", with cartilaginoid infiltration, painless on palpation. Regional lymph node is enlarged, of tight elastic consistency, painless, mobile. What is the most likely diagnosis?