This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Which of the following parotid gland tumor shows a hot spot on tc99 pertechnate scan? \nSelect and explain. \nA. adenolymphoma, B. adenoidcystic ca, C. acinic cell ca, D. Adenocarcinoma', 'role': 'user'}, {'content': "Answer: A \nExplanation: 99mTc (pertechnetate ion) is distributed like Cl- and is concentrated in the salivary glands and then secreted in the saliva. Therefore sodium pertechnetate (Na99mTcO4) is used to;\n(a) scan the salivary glands, especially the parotids; and\n(b) assess salivary gland function.\nAll salivary tumours produce a 'cold' spot on 99mTc (technetium) scan except adenolymphoma (Warthin's tumour) and Oncocytoma. They take up more isotope than the rest of the gland to give a 'hot' spot on the scan, so that a definite pre-operative diagnosis can be made without biopsy", 'role': 'assistant'}]