Maruyama N, Sasaki T, Arasaki A, Matsuzaki A, Nakasone T, Teruya T, Matayoshi A, Maruyama T, Karube K, Fujita J, et al. Thymoma appearing 9 years after the resection of squamous cell carcinoma of the lip: A case report of triple primary tumors and literature review. Oncology letters. 2019. 18. 3. 2777-2788