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Hello, everyone.

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Sidney Levy here, continuing our discussion

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of N staging of oral cavity malignancy.

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This vignette is concerned with the N staging, according

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to the most recent American Joint Cancer Committee 8th

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edition guidelines published at the beginning of 2018.

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There was a major change compared with the

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7th edition, and that consisted of splitting

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N staging according to whether the patient

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was human papillomavirus positive or negative.

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Now the background to this is that in recent years there

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has been a marked increase in the prevalence of squamous

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cell malignancy of the oropharynx or the oral cavity in

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a younger demographic who were typically not smokers

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or drinkers of excessive alcohol.

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These patients have been found to be human

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papillomavirus positive or HPV positive, and their

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tumors tend to have a slightly different morphology

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and a different prognosis, with appropriate

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treatment, usually a better prognosis.

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So as a result, the AJCC has

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redefined N staging into two groups.

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I'm going to begin by describing the HPV negative

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group, which are the traditional group of people

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who smoke or have drunk excessive alcohol.

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So N1 according to this definition is a

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single ipsilateral nodal metastasis, which

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is less than or equal to three centimeters.

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N2a is a single

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ipsilateral nodal metastasis, which is greater than three

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but less than or equal to six centimeters.

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N2b is multiple

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ipsilateral nodal metastasis, which all

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measure less than or equal to six centimeters.

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N2c is bilateral or contralateral nodal metastasis,

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which are less than or equal to six centimeters.

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N3a is any nodal metastasis, which

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measures greater than six centimeters.

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N3b is a definition which

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consists of any nodal metastasis

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which demonstrates a poorly defined blurred or

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infiltrative margin suggestive of extranodal extension.

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It is important that the diagnosis of

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extranodal extension is not purely radiological.

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There must be clinical evidence of it,

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such as a fixed lymph node on palpation.

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But, as a radiologist, you may raise suspicion

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of it if there is an infiltrative or blurred

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margin of a morphologically abnormal lymph node.

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So that's HPV negative disease.

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HPV positive disease is slightly simpler.

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N1 is an ipsilateral nodal metastasis, but instead of

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less than 3 cm, it can be less than or equal to 6 cm.

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N2 is not split up into N2A, N2B, and N2C.

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It is one N2 category, which consists of bilateral or

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contralateral nodal metastases less than or equal to 6 cm.

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N3 is also not split up and consists of a

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nodal metastasis greater than six centimeters.

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And lastly, with regards to M staging, the presence

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of distant metastasis in any organ, usually either

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bone, lung, or liver for the head and neck squamous

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cell malignancies is classified as M1 disease.

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So in summary, there have been major

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changes to the N staging of oral cavity

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and indeed head and neck squamous cell malignancy as of

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the beginning of 2018, which we need to be familiar with.

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The most important change is that N staging is

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determined according to human papillomavirus status.

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There is a different staging system

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for positive and negative HPV patients.

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In addition, the presence or absence of extranodal

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extension, morphologically, but particularly clinically,

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is a key factor in upgrading N staging

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to N3b for HPV negative disease.