A 47-year-old man complains of an ulcer on the back of his tongue. Hist history states that before the ulcer, there. was a tuberculous infiltrate for a long time. The infiltrate was gradually enlarging and then an ulcer formed. Objectively. there is a shallow elongated ulcer on the dorsum of the patient's tongue. The ulcer is painful, has overhanging edges and is surrounded with tubercles. Make the provisional diagnosis.