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Hello everyone.

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Dr. Sidney Levy here.

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Today we are continuing our discussion of the diagnosis

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and staging of oropharyngeal squamous cell malignancy.

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I would like to focus on the N staging today.

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We have a sample case here with pre-contrast T1

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without fat suppression, T2-weighted imaging with

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fat suppression, and post-contrast sagittal T1

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weighted imaging with fat suppression on the right.

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This is a base of tongue squamous cell malignancy with

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a single abnormal right level 2A cervical lymph node.

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How do we stage these tumors?

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The first thing to say is that, uh, we cannot

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stage it accurately unless we know whether the

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tumor is human papillomavirus positive or negative.

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And that is information which is often not available

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to the radiologist at the time of reporting.

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So, if you are going to N stage a tumor in this region,

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you need to qualify it by saying whether it is HPV positive,

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in which case it has a certain N stage, or whether it

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is HPV negative, in which the N stage may be different.

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General principles for HPV negative disease,

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we have N1, N2A, N2B, N2C, N3A, and N3B.

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N1 disease.

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N2A is a single ipsilateral lymph node

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which measures less than three centimeters.

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Just like this case we have here as an example.

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We need to measure the lymph node in its

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greatest dimension, which is often in the

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superoinferior dimension, as in this case.

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N2A disease is a single ipsilateral lymph node.

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which measures more than

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3 centimeters, but less than 6 centimeters.

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N2B disease is multiple ipsilateral lymph

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nodes, which measure less than six centimeters.

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N2C is bilateral or contralateral to the side of primary

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tumor lymph nodes that measure less than six centimeters.

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N3A disease is any lymph node that measures

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more than six centimeters, and N3B disease

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is a new consideration as of the most recent guidelines in

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which we take into account the concept of extranodal extension.

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I would like to elaborate on this.

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Extranodal extension is strictly a clinical or

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pathological assessment of whether the nodal disease has

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infiltrated into surrounding fat or other soft tissue.

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If it is present, then a tumor is automatically

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staged as N3B, irrespective of lymph node

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measurements or the position of the lymph node.

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So it's a very important concept to look for.

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I'm going to use this particular

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lymph node to demonstrate its absence.

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This lymph node has a well-circumscribed

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margin where you can see the edge of the lymph

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node distinctly from the adjacent fat plane.

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If, however, the lymph node demonstrated spicules,

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or a blurred margin, or an infiltrative irregular

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margin, spreading into the adjacent soft tissue,

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that is what constitutes extranodal extension.

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And that would automatically upgrade the

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N stage to N3B for HPV negative disease.

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For HPV positive disease, the staging is slightly different.

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And the reason for that is the prognosis

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for these tumors is also different.

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The good news is it's simpler.

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So, for N1 disease, in HPV positive oropharyngeal or

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oral cavity malignancy, in this particular case, if

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the tumour is a HPV positive tumour, the end staging

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remains the same, because we have an ipsilateral

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nodal metastasis, which is less than 6 centimetres.

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In HPV positive disease, N2 disease is considered

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bilateral or contralateral nodal metastasis, which

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measures less than or equal to 6 centimetres.

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And lastly, N3 disease is nodal

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metastasis greater than 6 centimetres.

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So, in summary, the end staging of oropharyngeal

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malignancy is completely determined by the presence

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or absence of human papillomavirus within the tumor.

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And it is important to be aware that this is a change

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compared with the 7th edition of AJCC guidelines.

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And now, I is in effect as of the

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beginning of 2018 with the eighth edition.

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In our next vignette, we will go on to formally

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stage this tumor from a perspective of TNM.