This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
Which of the following parotid gland tumor shows a hot spot on tc99 peechnate scan? 
Select and explain. 
A. adenolymphoma, B. adenoidcystic ca, C. acinic cell ca, D. Adenocarcinoma
A: adenolymphoma
Answer: A: adenolymphoma 
Explanation: 99mTc (peechnetate ion) is distributed like Cl- and is concentrated in the salivary glands and then secreted in the saliva. Therefore sodium peechnetate (Na99mTcO4) is used to; (a) scan the salivary glands, especially the parotids; and (b) assess salivary gland function. All salivary tumours produce a 'cold' spot on 99mTc (technetium) scan except adenolymphoma (Wahin'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