A 37-year-old woman complains of a tumor on her lower lip on the surface that faces the oral cavity. The tumor appeared approximately 2 weeks ago, gradually enlarges, and makes lip movement problematic. Objectively, within the lower lip there is a circumscribed round elastic painless induration fused to the mucosa. The mucosa over the induration is transparent, while around the induratuion it remains unchanged. The regional lymph nodes are not enlarged. What is the most likely diagnosis in this case?