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Hello everyone, Sidney Levy here, continuing our

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discussion of oral cavity squamous cell malignancy,

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specifically a floor of mouth squamous cell carcinoma.

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I'd like to T-stage the tumor with you today.

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First things first, we need to take some measurements.

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This is a large tumor and it'll either

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be the coronal or the sagittal projection

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that will provide the greatest dimension.

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But, uh, we can already say just by looking at it that

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this lesion is extensive and well over 4 cm.

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So, it's already into the at least

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moderately advanced category.

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The next thing to say is depth of invasion.

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Again, not really at issue here.

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This is well over ten millimeters depth of invasion.

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So, that criterion is well and truly satisfied.

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We're now into criteria of advanced disease.

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And in particular, the next thing to look at is bone.

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So, I'd like to point out to you, as discussed in

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more detail in a specific vignette, that this lesion

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has marrow infiltration on the left-hand side.

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So I've got T1-weighted imaging on the left, and

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you can see that, uh, the marrow is clearly abnormal

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compared with the normal contralateral side.

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So we've established that there's mandibular

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cortical invasion and marrow infiltration.

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Next thing to think about is,

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is there perineural infiltration.

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And because it's the mandible, we think of the

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inferior alveolar nerve, which is a branch of the

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mandibular division of the trigeminal nerve, or V3.

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In order to do that, we need to look at a

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combination of pre-contrast T1 and post-contrast T1.

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And I find either the coronal

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or axial projection most useful for this.

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So the first thing you need to do is to identify the normal

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nerve on the opposite side to give yourself a landmark.

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That's here.

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Then we need to assess the opposite side.

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Now the first thing you can see is,

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it's hard to see the nerve on the left-hand side.

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So there is loss of the normal plane between

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the nerve and the margin of the mandibular canal

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within which the inferior alveolar nerve resides.

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So, this is all blurred and indistinct.

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There's abnormal enhancement of

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the marrow around this region.

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You can see what is or was the canal, but you can't

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really distinguish the nerve very easily at this site.

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In places where you would normally be

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able to see the nerve quite well, you have

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nothing but indistinct marrow architecture.

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So this is all suggestive of inferior alveolar

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nerve perineural infiltration on the left-hand side.

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You need to go back further and have a look in an

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advanced case like this to see whether the mandibular

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nerve itself just demonstrates perineural infiltration.

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In this case, it doesn't, but it's always important to

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keep in mind that you need to go all the way back

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to the cavernous sinuses in order to establish that.

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And that might be the case with either the

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mandibular nerve or the maxillary nerve.

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64 00:03:17,160 --> 00:03:17,239

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i.e. V2 maxillary division of trigeminal nerve.

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In this case, that's not applicable,

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but we do have an advanced tumor.

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We need to think about the advanced local disease criteria.

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Does this tumor invade into the masticator space?

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The answer to that question is no.

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It actually doesn't reach that far, and

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just to show you the masticator space,

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it's here, and the tumor is well below it.

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Does the tumor reach as far back

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as the internal carotid artery?

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Nowhere near it.

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So, we are dealing with a moderately advanced

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tumor, which has invaded the mandibular cortex and

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is almost certainly associated with inferior

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alveolar nerve perineural infiltration.

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It's a large tumor.

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In times past, we would have gone into great

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detail describing the extrinsic tongue muscles

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that have been infiltrated by the tumor.

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86 00:04:16,904 --> 00:04:21,065 But remember, in the most recent edition of staging

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guidelines, depth of invasion has superseded all of that.

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So this tumor is more than 10 millimeters deep or thick.

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Therefore, it is already an advanced tumor.

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But for the record, most of the extrinsic tongue

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muscles, including mylohyoid, genioglossus,

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hyoglossus, and probably geniohyoid, are infiltrated.

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And this tumor's actually gone all the way underneath

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the mandible, and out the side along the buccal space.

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So, very extensive local spread.

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In summary, the T staging of this tumor is a

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T4A tumor due to the fact that it has invaded

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the mandible, but you also need to mention it's a

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bilateral tumor that's crossing the midline.

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It has spread into the oral tongue superiorly.

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It has spread into the sublingual space,

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under the mandible into the left buccal space

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and there is likely perineural infiltration

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of the inferior alveolar nerve on the left.

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So, a very extensive tumor.

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In our next vignette, we will N stage the tumor.