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This is a patient who had a palpable abnormality in

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the left side of the neck who was HIV positive.

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On the T1-weighted scan, we see that the patient has

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had a marker placed over the palpable abnormality

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and this corresponds to a lesion which is in

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the parotid gland on these VIBE images.

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Now, at first blush, you would look at this and say,

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well, there is not the same signal intensity as the CSF.

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So I wouldn't necessarily suggest that this

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is a cyst. When you do the cyst image,

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the constructive interference in a steady state,

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you see that the lesion is dark in signal

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intensity and that is worrisome.

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Now we go to the post-gadolinium enhanced scan and

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we see that there is absence of contrast enhancement

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except in the periphery of this lesion.

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We're going to scroll up above and we see

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it's a solitary lesion in this patient.

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So what is this?

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It's got dark signal intensity on cyst and it's not

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necessarily like CSF on the T1 VIBE image.

1:08

Well, this is one of the lessons about not being confused

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by cyst imaging. The fluid here, if it is an assist,

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and I believe it's an assist,

1:17

is likely to have high protein and therefore it

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looks dark and you worry about a malignancy.

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But let's look at the STIR image.

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Remember that CISS is not just a T2-weighted

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sequence. It's got other qualities to it.

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Contrast that with this on the STIR image,

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you see that this lesion has dark signal intensity.

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Now, I'm more reliable that it's not a traditional cyst

1:48

in the parotid gland. So what could this be?

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This is a high protein content cyst.

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You notice that it is slightly

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bright on T1-weighted scan,

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it's dark in T2-weighted scan

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because of the high protein.

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And this might be the presence of

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lymphoid material within the cyst because this did

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get aspirated and actually removed and

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this was a lymphoepithelial cyst.

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Let's just make sure on the delayed contrast

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enhanced scans that you don't see any contrast

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being imbibed into the mass,

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but that was not the case in this patient.

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So a lymphoepithelial cyst showing

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high protein content,

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that is not unusual when you have

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lymph in the actual cyst itself.