Interactive Transcript
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Hello, everyone.
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Sidney Levy here, continuing our discussion on the diagnosis
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and staging of oral cavity squamous cell malignancy.
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I'd like to focus on our case of right
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mandibular alveolar mucosal squamous cell carcinoma.
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I have axial and coronal post-contrast
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T1-weighted imaging with fat suppression.
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And we will now outline the tumor.
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The first thing I'm going to do is
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to take a maximal measurement of it.
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Remember that you need to look at all three projections
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to decide which is the maximal dimension.
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In this case, it's coronal.
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So the tumor is coming back at about three centimeters.
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The next measurement we need to
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make is the depth of invasion.
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Keeping in mind that the alveolar
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mucosa is situated there.
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So therefore, the depth of invasion in either direction
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is well over 10 millimeters, which is a key threshold.
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So we've got two out of the three ingredients that
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we need in order to be able to T stage this tumor:
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the maximal tumor dimension and the depth of invasion.
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The last feature, which is important,
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is whether it is invading adjacent structures.
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Remember, alveolar mucosal oral cavity malignancy invades
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bone early, and the reason for that is that
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the gingival mucosa is attached to the underlying alveoli,
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so there isn't much room, and it's quite easy for these
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tumors to burrow into adjacent mandible or maxilla.
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This tumor has done that.
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And that automatically makes it at
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least moderately advanced disease.
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To T stage this tumor, as the tumor is less than 4 cm
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but more than 2 cm, and it has a depth of invasion of
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more than 10 mm, it is automatically at least a T3 tumor.
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However, because it has direct cortical invasion of the
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mandibular cortex, it is upgraded to T4A automatically,
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40 00:02:14,215 --> 00:02:16,075 i.e. moderately advanced disease.
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The last step is to decide whether it is very
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advanced, and in this case, it is not, because
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it has not invaded the masticator space.
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So let me just help demonstrate that
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for you on this post-contrast imaging.
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The masticator space is back here, and the tumor is
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confined to the oral cavity and the adjacent buccal space.
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So it has invaded the buccal space,
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but not the masticator space.
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And this is where it's invading the mandibular cortex.
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So, T4A tumor with mandibular cortical invasion.
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One last thing that we need to make a comment on, although
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it is not a formal component of the staging system,
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is the presence or absence of perineural invasion.
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Because once these tumors invade bone, they can invade
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the nerves which are situated within these bones.
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So, in order to do that, I personally use pre-contrast
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T1-weighted imaging without fat suppression and post-
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contrast T1-weighted imaging with fat suppression.
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In the mandible, the nerve in question
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is the inferior alveolar nerve.
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So, the inferior alveolar nerve is situated here and here.
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Now, in order to decide whether it's involved or not, it's
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always helpful to compare it with the contralateral side.
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So, I'm just going to zoom out a little bit,
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and we're going to focus on the nerves.
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There are two things that I look for to help me decide
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whether there is perineural invasion present or not.
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Is there abnormal thickening on
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pre-contrast T1-weighted imaging?
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And is there abnormal enhancement of the
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nerve on post-contrast T1-weighted imaging?
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In this case, we need to compare
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with the contralateral side.
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We don't see any obvious thickening of the right
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inferior alveolar nerve here, compared with the left.
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However, we do notice that there is some enhancement,
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particularly in the segment of the nerve adjacent
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to the tumor, which raises suspicion, but isn't
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completely diagnostic for perineural invasion.
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And the reason I say that is that the enhancement
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is predominantly peripheral, and enhancement at the
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periphery of a nerve can be related to perineural
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venous vasculature, small venules around the nerve.
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So what you really want to see is enhancement within the
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nerve in order to be sure that it's perineural infiltration.
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But because this nerve is so close to the tumor,
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and there is some asymmetric enhancement at the
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periphery, I would raise suspicion of inferior
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alveolar nerve perineural infiltration, and that
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will help guide the pathologist towards that to look
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carefully for it at the time of a surgical resection.
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So in summary, this tumor does not have any abnormal
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lymphadenopathy within the head and neck, and there was no
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evidence of distant disease on the MRI that was performed.
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So in summary, this tumor is a T4aN0M0 tumor.
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98 00:05:32,495 --> 00:05:33,004 Thank you.
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