This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oral Cavity, Subject name: Surgery
[{'content': 'A 59-year-old woman has discomfort in the posterior part of her tongue. A biopsy confirms that the lesion is a carcinoma. What is true in carcinoma of the posterior third of the tongue? \nSelect and explain. \nA. Lymphoid tissue is absent., B. Lymph gland spread is often encountered., C. There is an excellent prognosis., D. The tissue is well differentiated.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Carcinoma of the posterior third of the tongue is often detected late and carries a worse prognosis. Posterior-third tongue tumors are also called lymphoepitheliomas. These lesions can be poorly differentiated.', 'role': 'assistant'}]