Hypopharynx

Mostly unchanged from the 7^th Edition.
T0 has been removed as a category
T3 criteria have been changed from "extension to esophagus" to "extension to esophageal mucosa." T4a criteria now includes invasion of esophageal muscle.
This staging system now uses the new shared nodal and group staging described previously.

T Category	Criteria
TX	Primary tumour cannot be assessed
Tis	Carcinoma in situ.
T1	2 cm or smaller in greatest dimension *AND* involving 1 subsite of the hypopharynx only.
T2	>2 cm - 4 cm in greatest dimension. OR involvement of more than 1 subsite of the hypopharynx.
T3	> 4 cm in greatest dimension. OR fixation of the hemilarynx. OR extension to the mucosa of the esophagus.
T4	Moderately advanced (T4a) or very advanced (T4b) disease
T4a	Moderately advanced local disease Tumour invades thyroid/cricoid cartilage, hyoid bone, thyroid gland, esophageal muscle or central compartment soft tissue. Central compartment soft tissue includes prelaryngeal strap muscles and subcutaneous fat.
T4b	Very advanced local disease Tumour invasion of the prevertebral fascia, carotid artery encasement, or involves mediastinal structures.

To be categorized as T1 a tumour has to be ≤2 cm and involving 1 subsite of the hypopharynx only.
To be categorized as T2 a tumour has to be either >2 - 4 cm or involving 2 or more subsites of the hypopharynx.
Similar to in the larynx, vocal fold fixation (fixation of the hemilarynx) upcategorizes to T3
Involvement of the esophageal mucosa upcategorizes to T3, while involvement of the esophageal muscle upcategorizes to T4a
T4a is also defined by extension essentially to any of the structures in the central neck (thyroid gland, cricoid/thyroid/hyoid, straps, or central compartment fat).

N Category	Criteria
NX	Regional lymph nodes cannot be assessed.
N0	No regional lymph node metastasis.
N1	Single ipsilateral lymph node that is 3 cm or less in maximal dimension without extranodal extension
N2
N2a	Single ipsilateral lymph node that is > 3 cm but ≤ 6 cm in maximal dimension without extranodal extension
N2b	Mulple ipsilateral lymph nodes that are ≤ 6 cm in maximal dimension without extranodal extension
N2c	Bilateral or contralateral lymph nodes that are ≤ 6 cm in maximal dimension without extranodal extension
N3
N3a	Metastasis in any lymph node > 6 cm without extranodal extension
N3b	Metastasis in any lymph node with clinically overt *extranodal extension.*

N Category	Criteria
NX	Regional lymph nodes cannot be assessed.
N0	No regional lymph node metastasis.
N1	Single ipsilateral lymph node that is 3 cm or less in maximal dimension without extranodal extension
N2
N2a	Single ipsilateral lymph node that is > 3 cm but ≤ 6 cm in maximal dimension without extranodal extension
	OR metastasis to a single ipsilateral lymph node that is 3 cm or less in maximal dimension *WITH extranodal extension*
N2b	Mulple ipsilateral lymph nodes that are ≤ 6 cm in maximal dimension without extranodal extension
N2c	Bilateral or contralateral lymph nodes that are ≤ 6 cm in maximal dimension without extranodal extension
N3
N3a	Metastasis in any lymph node > 6 cm without extranodal extension
N3b	Metastasis in any lymph node with clinically overt *extranodal extension.*
	*EXCEPT* if it a single ipsilateral node that is 3 cm or less with extranodal (which would instead be categorized as N2a as above).

Uses the Shared Nodal Staging System described previously.
If a patient has any clinical extranodal extension, they are automatically be categorized in the maximum possible N sub-category (N3b).
Pathologic N categorization is almost the same except for the isolated situation of having a single ipsilateral lymph node that is 3 cm or less with ENE identified only on pathology.
- Instead of being up-categorized to N3b, this specific case is up-categorized to N2a instead.
- In all other situations where there is ENE (clinical or pathologic), they are still up-categorized to N3b.
Clinically the AJCC defines ENE as invasion of skin, infiltration of musculature/fixation to adjacent structures on clinical examination, cranial nerve, brachial plexus, sympathetic trunk or phrenic nerve invasion with dysfunction.

Pathologically, ENE is defined as extension of metastatic tumour beyond the confines of the lymph node itself.
Clinically the AJCC defines ENE as invasion of skin, infiltration of musculature/fixation to adjacent structures on clinical examination, cranial nerve, brachial plexus, sympathetic trunk or phrenic nerve invasion with dysfunction.

M Category	Criteria
M0	No distant metastasis
M1	Distant metastasis present

Uses the Shared Group Staging System described previously.
Straightforward to remember due to the pattern seen above when creating a table against the T and N staging.
(T1 N0) is staged as Stage I, and (T2, N0) is staged as Stage II. Thereafter, each increasing stage is immediately to the right and below the previous stage.