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Hello, everyone.

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Dr. Sidney Levy here, continuing our discussion

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of oropharyngeal squamous cell malignancy.

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In this vignette, I would like to show you a

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differential diagnosis of squamous cell carcinoma,

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which we had the benefit of recognizing that

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there were atypical features at the time

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of reporting the study, but really it was

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the pathology that gave it away in the end.

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This is a base of tongue tumor,

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which was initially reported

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as a squamous cell carcinoma,

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but in retrospect, uh, ended up being a mucoepidermoid

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minor salivary gland malignancy of the base of tongue.

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And I'd like to show it to you because there are

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a couple of atypical features which would make you

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question the diagnosis of squamous cell carcinoma,

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even if you couldn't be dogmatic about calling it, uh,

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a different sort of, uh, head and neck malignancy.

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So I have, uh, T2-weighted imaging in

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the axial projection on the left and the

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same thing in the coronal projection.

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And then I've just got a localizer,

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sagittal T1, just to show you that we

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are at the level of the base of tongue.

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So I'll draw the tumor for you.

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What can we say about it?

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It's an ulcerative tumor.

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It's a midline tumor.

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And there's a couple of other features

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that are interesting about it.

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We can see the mucosa

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of the base of tongue very well, and normally

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that's involved with the tumor because, remember,

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squamous cell malignancies arise from the mucosa

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of the oral cavity or the pharynx or the larynx.

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This tumor is actually centered deep to the mucosa

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rather than within the submucosal space, if you like.

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So that's the first clue that we might not be

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dealing with a standard squamous cell carcinoma.

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The next thing to keep in mind as we look

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at it is there are these unusual central

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cystic structures, which are not really a

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typical feature of squamous cell carcinoma.

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Now, you may see areas of necrosis

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centrally within a squamous cell tumor.

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But, once again, an atypical

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feature, something to think about.

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These two features, which I've just illustrated for

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you, being the clear definition of the mucosa of

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the base of tongue, and also the unusual cystic

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morphology within the center of the tumor,

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should be enough for you to at least think that

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this may not be a typical squamous cell carcinoma.

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Now, I wouldn't necessarily be dogmatic and say, "This

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is a minor salivary gland malignancy," because these

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tumors are rare, particularly in the base of tongue.

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But it's just worth mentioning that this is

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the sort of study that is worth following up to

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determine pathology and to see whether it was

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in fact a standard squamous cell malignancy.

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The last thing to mention is, when you come across

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a tumor that is atypical, it is still permissible

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to stage it according to the staging guidelines

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that we have used for head and neck squamous cell

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malignancy, even if later on it becomes apparent

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that it is a minor salivary gland malignancy.

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So in summary, keep in mind that minor salivary

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gland malignancies often mimic squamous cell

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malignancy and can be only determined in many cases

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at the time of pathological analysis of tissue.

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There are a couple of clues to help you, and perhaps

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the biggest clue is that the tumors tend to be

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centered in the submucosal space where the minor

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salivary glands reside, rather than the mucosa itself.

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And you can often see a clean

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mucosa overlying these tumors.

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This one happened to be a mucoepidermoid

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carcinoma, but adenoid cystic

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carcinoma, if anything, is more common.

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It's worth keeping in mind common sites where

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minor salivary gland malignancy may reside,

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and these are typically in the floor of mouth,

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the soft palate, the parapharyngeal space, including

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the parapharyngeal fat, and the hard palate.