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Hello everyone.

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Dr. 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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We're currently focused on the retromolar trigone.

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And I have our example case of a retromolar trigone

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squamous cell malignancy, which we're now going to stage.

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So firstly, we need to get some measurements.

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The lesion is here, T1 hypointense on pre-contrast T1.

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Enhancing on post-contrast T1-weighted imaging.

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More difficult to see on the sagittal, but also enhancing.

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So let me outline it for you.

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The lesion is here on the axial projection, here on the

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coronal projection, and here on the sagittal projection.

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So you can see that it doesn't just involve the

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mandibular portion of the retromolar trigone,

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it also extends up towards the maxillary portion here.

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Now from our measurements, we can tell that it is

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a tumor that is in between 2 and 4 centimeters.

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In regards to our next measurement, which we

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need to establish, its depth of invasion is less

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than 10 millimeters but more than 5 millimeters.

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So that can be established on multiple planes.

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It is always worth checking on

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more than one plane to be sure.

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The next thing we need to establish after

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taking our measurements is whether there

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has been invasion of adjacent structures.

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And specifically I'm talking about the

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cortical bone of the maxilla or mandible.

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And in this case it is subtle, but there

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is invasion of the

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mandible adjacent to the lesion, just here.

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And if we cross-reference, you can see

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on the post-contrast imaging, that the normal

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contour of the mandible is lost at that site.

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You can even establish it on the sagittal

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imaging because of the fine slice thickness.

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So unequivocally, this tumor is invading the adjacent mandible.

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Once we've established that, we know that this tumor

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is a moderately advanced tumor, specifically a T4A

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tumor with a depth of invasion greater than 10 mm.

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Although the tumor is quite small,

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it's less than 4 cm, it has concerning features.

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The other thing to report with these tumors is which

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spaces do they involve apart from the retromolar trigone.

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And in this case, the tumor is extending forward

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into the alveolar and buccal mucosa, and it is also

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starting to show some extension medially towards the

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ipsilateral junction of the base of tongue and oral tongue.

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This is the junction of the base of tongue

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posteriorly and the oral tongue anteriorly.

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So, this tumor is actually quite advanced

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and is concerning for multiple reasons.

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It does not demonstrate perineural infiltration, which is

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another important feature that we need to look for.

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And it doesn't demonstrate features of very

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advanced disease, such as extending into the

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masticator space or the pterygoid plates.

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So in summary, this tumor is a T4A tumor,

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and in this particular case, it did not demonstrate

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any nodal metastasis or distant metastasis.

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So it's actually N0 and M0.

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But, there was marrow infiltration of the

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adjacent mandible, and spread in multiple

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directions, including forward, into

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the buccal and alveolar mucosal space, as well as medially into

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the base of tongue/oral tongue, and laterally,

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starting to head out laterally into the buccal space.

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These tumors tend to metastasize widely and

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often present with advanced nodal metastases.

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This patient has not presented that way,

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butit's very important when staging these tumors

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to be comprehensive in assessment of marrow,

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perineural infiltration, and spread into adjacent spaces.