Oncocytoma
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Oncocytomas are not very common lesions.
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Certainly, the benign lesions of the parotid gland
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are dominated by pleomorphic adenomas
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and Warthin's tumors. However,
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this is my one teaching file case of an oncocytoma.
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And it shows relatively nicely the finding of a
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vanishing tumor. So here on the T1-weighted scan,
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we see the lesion very nicely,
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and we're going to describe it in the superficial
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portion of the parotid gland.
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We don't see any malignant lymphadenopathy.
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We don't see any approaching of the normal
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appearance of the stylomastoid foramen.
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We look at it on T2-weighted
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scan and it's not lighting up the way a
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pleomorphic adenoma lights up.
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Therefore, we're going to recommend a biopsy.
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If it lights up like a bulb,
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the way pleomorphic adenoma does,
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then we suggest that it's a pleomorphic adenoma
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and the surgeons may go in even without doing
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a biopsy. On the post-gadolinium-enhanced scan,
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we have that phenomenon of the "vanishing tumor."
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So although this enhances slightly more
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than the normal parotid tissue,
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you can see that you lose the conspicuity of the
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lesion, and therefore it seems to be vanishing
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from its T1 appearance.
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And this is the feature that people have
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described with the oncocytoma.
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On the coronal post-gadolinium-enhanced scan,
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we've gotten a little bit more time
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for the tumor to imbibe contrast,
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but nonetheless,
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its contrast with the normally enhancing
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parotid tissue is limited.
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Hence the term "the vanishing parotid tumor"
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equals oncocytoma.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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