Key updates from the UICC TNM classification of malignant tumours

05 January 2026

The Union for International Cancer Control (UICC) published the 9th Edition of the TNM classification of malignant tumours in August 2025, with recommended implementation to commence from 1st January 2026. Whilst most tumour sites remain unchanged from the 8th edition, several key alterations and refinements have been made, many affecting sites in the head and neck. As always, these changes are made considering new data focusing on prognosis of these tumours and it is recommended that MDTs should update and familiarise themselves with these adaptations.

Mucosal lip and oral cavity

Site alterations:

Refinement of the lip and oral cavity subsite has been made to only include those carcinomas arising from mucosal sites. As such, carcinomas of the dry lip and vermillion are now classified under head and neck skin rather than lip and oral cavity. Minor and major salivary glands are now also reclassified together under a broader salivary gland section.

Depth of invasion:

Depth of invasion was an important addition implemented within UICC TNM 8th edition and we now see clarification and expansion of this with tumours >4cm in greatest dimension and >10mm in depth now classified as T4a. Superficial erosion of the dry lip and vermillion is not sufficient to be classified as T4a.

Extranodal extension (ENE):

The presence of extranodal extension was another big update featured within the UICC TNM 8th edition, which is further refined within this latest update, aiming for more specific identification regarding tumours known to be associated with poorer prognosis. It is now recommended that imaging is the standard method of detecting unequivocal clinical extranodal extension (iENE), which MDTs should consider when determining clinical staging. Pathological assessment of extranodal extension (pENE)is also further refined to only those where tumour definitively transgresses through the entire thickness of the lymph node capsule into the surrounding connective tissue.

Nasopharynx

TNM updates:

One of the main updates within the UICC TNM 9th edition affects carcinomas of the nasopharynx. The T stages have been clarified, in particular, involvement of the inferior orbital fissure is now classified as orbital invasion. Overall nodal staging is simplified to Nx, N0, N1, N2 and N3 without subcategories, dictated not only by metastasis size and laterality but also the presence of extranodal extension. Distant metastases are subclassified into either M1a or M1b dependent on the number of lesions present (M1a <3 distant lesions, M1bL >3 distant lesions).

Stage grouping:

Stage I is expanded to include IA and IB, differentiating between T1 and T2 with and without nodal disease. Stage IV is also subcategorised to demonstrate differences to distant metastases within either M1a or M1b categories.

Oropharynx

Terminology changes:

Classification is no longer simply based on p16 expression but more explicitly on HPV status and carcinomas of the oropharynx should now be classified as ‘HPV associated’ or ‘HPV independent’. This is in line with the anticipated guidance changes from the Royal College of Pathologists outlining the requirement for both p16 and HPV specific testing for diagnosis of an HPV associated oropharyngeal squamous cell carcinoma. Additionally, there is now no recognition of in situ carcinoma of HPV associated tumours as the basement membrane of the tonsillar crypts is incomplete and those previously classified as Tis should now be staged as T1, resulting in removal of Stage 0 groupings.

Local and distant spread:

Clinical nodal staging changes follow those of the nasopharynx, importantly incorporating extranodal extension, however final pathological staging still considers the number of positive nodes with more thresholds than seen previously in the 8th edition.

Salivary glands

TNM updates:

Minor salivary glands are now no longer staged according to site within the oral cavity, but together with major salivary glands in their own salivary gland category. As salivary gland sites now exist over a broader head and neck area, the cT4 staging has been expanded to reflect this, subcategorising cT4 salivary tumours into those that invade immediately adjacent sites (cT4a) and those invading beyond adjacent structures (cT4b).

There have been major changes to nodal staging for salivary gland tumours. Nodal staging is simplified with removal of pN3a/b categories and staging is to be determined by nodal number and not lymph node size or locality. We also see a downgrading of some stage groupings with

Stage IV A and B subcategories restaged into Stage III A and B in the UICC TNM 9th edition. Only tumours with distant metastatic disease meet Stage IV criteria.

Parathyroid glands

For the first time, staging for parathyroid gland carcinomas is now documented with the formation of a brand-new chapter in the UICC TNM 9th edition.

Overview of changes

Overall, UICC TNM 9th edition follows many trends set out within the UICC TNM 8th edition, with a continued emphasis on depth of invasion and extranodal extension featuring more broadly across tumour sites. Whilst there are fewer major alterations to those introduced in the previous edition, the updated TNM staging still aims to enhance prognostic accuracy and MDTs are encouraged to be diligent over the subtle updates to ensure correct patient staging.

Dr Lisette Collins

Pathology Representative, BAHNO Council
Consultant Oral and Maxillofacial Pathologist

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