Which of the following parotid gland tumor shows a hot spot on tc99 pertechnate scan?

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; (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 (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