A 53-year-old patient complains of an ulcer on the lateral surface of the tongue. The ulcer appeared 6 months ago in the result of a trauma caused by sharp tip of the 37 tooth metal crown. A dentist replaced the crown with the one of better quality and prescribed keratoplastic drugs. Despite these measures the ulcer continues to grow. Lately there has been pain during talking, chewing, swallowing; sometimes the pain irradiates to the pharynx. Objectively: on the lateral surface of the tongue there is a painful ulcer with uneven raised dense margins and lumpy floor covered with grayish necrotic coating. What diagnosis is most likely?