Definition / Overview
Head and neck squamous cell carcinoma (HNSCC) encompasses a heterogeneous group of malignancies arising from the mucosal lining of the upper aerodigestive tract. The major subsites are the oral cavity, oropharynx, larynx, hypopharynx, and nasopharynx; each has distinct epidemiology, lymphatic drainage patterns, staging criteria, and treatment philosophy. Accurate assessment and staging directs multidisciplinary management, predicts prognosis, and determines whether single-modality or combined-modality treatment is required.
Key shared risk factors:
- Tobacco (smoked and smokeless) and alcohol: synergistic carcinogenic effect
- Human papillomavirus (HPV), predominantly type 16: oropharyngeal SCC; HPV-positive disease carries a substantially better prognosis
- Epstein-Barr virus (EBV): nasopharyngeal carcinoma (NPC)
- Chronic sun exposure: lower lip SCC
- Plummer-Vinson syndrome: pharyngeal and oral mucosal malignancy risk
- Long-term immunosuppression (e.g. renal transplant recipients)
Staging Framework
TNM/AJCC Principles
All HNSCC is staged using the TNM/AJCC system. Staging integrates:
- T category: primary tumour size and/or extent of local invasion
- N category: number, size, and laterality of regional lymph node metastases
- M category: presence of distant metastases
The overall stage groups I to IVA/IVB/IVC guide treatment intensity:
| Stage | General Implication | Typical Treatment Approach |
|---|---|---|
| I-II | Localised disease | Single modality (surgery OR radiotherapy) |
| III | Locoregionally advanced | Multimodality (surgery + adjuvant, or definitive CRT) |
| IVA | Resectable advanced | Multimodality, often concurrent chemoradiotherapy |
| IVB | Unresectable/very advanced | Definitive CRT or palliative intent |
| IVC | Distant metastases | Palliative systemic therapy |
NPC uses a distinct N staging system because of its tendency for bilateral and retropharyngeal nodal spread; this is detailed below.
Subsite-by-Subsite Assessment and Staging
1. Oral Cavity
Anatomical Boundaries
The oral cavity extends from the vermilion border of the lip anteriorly to the hard palate-soft palate junction superiorly, the circumvallate papillae inferiorly, and the anterior tonsillar pillars laterally. Subsites include the lip, oral tongue (anterior two-thirds), floor of mouth, hard palate, buccal mucosa, retromolar trigone, and mandibular/maxillary alveolar ridges.
Clinical Features
- Ulcerative or exophytic mucosal lesion, often with induration
- Trismus suggests pterygoid involvement or mandibular invasion
- Ipsilateral neck mass; level I-III most common (submental, submandibular, upper jugular)
- Oral tongue: depth of invasion (DOI) is critical; tumours $\geq 4$ mm DOI warrant elective neck dissection for clinically N0 disease; tumours $\geq 2$ mm carry metastatic risk
- Floor of mouth: proximity to mandible governs resection planning
- Lower lip SCC: low rate of occult cervical metastasis ($< 15\%$), may observe in stage I/II with N0
T Staging (Oral Cavity)
| T Category | Criteria |
|---|---|
| T1 | $\leq 2$ cm, DOI $\leq 5$ mm |
| T2 | $\leq 2$ cm with DOI $> 5$ mm to $\leq 10$ mm, OR $2$-$4$ cm with DOI $\leq 10$ mm |
| T3 | $> 4$ cm OR any tumour with DOI $> 10$ mm |
| T4a | Moderately advanced: invades adjacent structures (cortical bone excluding alveolus, deep/extrinsic tongue muscles, maxillary sinus, skin) |
| T4b | Very advanced: invades masticator space, pterygoid plates, skull base, or encases carotid artery |
Note: Depth of invasion was formally incorporated into oral cavity T staging with the AJCC 8th edition and is now a defining criterion, not merely a prognostic factor.
Nodal Drainage
Primary: levels I, II, III. Advanced disease can reach levels IV and V. Bilateral drainage is common for midline floor of mouth and tongue lesions.
2. Oropharynx
Anatomical Boundaries
The oropharynx lies between the soft palate superiorly, the hyoid inferiorly, and the anterior tonsillar pillars anteriorly. Subsites: soft palate, palatine tonsil and tonsillar fossa, base of tongue (posterior one-third), and posterior oropharyngeal wall.
HPV and p16 Status
- HPV-positive oropharyngeal SCC (surrogate: p16 immunohistochemistry) has a distinct favourable prognosis and is staged separately in the AJCC 8th edition
- p16-positive disease typically presents in younger, non-smoking males; often with a small primary and a larger cystic neck node (level II)
- p16 testing is mandatory in all oropharyngeal SCC; positive p16 should trigger confirmatory HPV testing where required by the MDT
T Staging (Oropharynx, HPV-negative and HPV-positive differ only in N staging for the latter)
| T Category | Criteria |
|---|---|
| T1 | $\leq 2$ cm |
| T2 | $2$-$4$ cm |
| T3 | $> 4$ cm OR extension to lingual surface of epiglottis |
| T4a | Moderately advanced: invades larynx, deep/extrinsic tongue musculature, medial pterygoid, hard palate, or mandible |
| T4b | Very advanced: invades lateral pterygoid, pterygoid plates, lateral nasopharynx, skull base, or encases carotid artery |
HPV-Positive N Staging (distinct)
| N Category | Criteria |
|---|---|
| N1 | Unilateral nodes $\leq 6$ cm |
| N2 | Contralateral or bilateral nodes $\leq 6$ cm |
| N3 | Nodes $> 6$ cm |
Nodal Drainage
Primarily levels II, III, IV; retropharyngeal nodes at risk for base-of-tongue and soft palate lesions. Bilateral drainage common for midline and base-of-tongue primaries.
3. Larynx
Anatomical Boundaries and Subsites
| Region | Boundaries | Key Feature |
|---|---|---|
| Supraglottis | Epiglottis tip to laryngeal ventricles (upper margin) | Rich lymphatics; bilateral drainage |
| Glottis | True vocal folds, anterior/posterior commissure, upper ventricle floor | Sparse lymphatics; rarely spreads early |
| Subglottis | Below true cords to inferior border of cricoid | Rare primary site; can track to paratracheal nodes |
Clinical Features
- Dysphonia (glottic): often the earliest symptom, facilitating early detection
- Stridor: late; suggests critical airway compromise
- Dysphagia and referred otalgia (via Arnold's nerve): supraglottic
- Neck mass: supraglottic primaries; glottic spread only with advanced T3/T4 disease
T Staging (Larynx, Supraglottis)
| T Category | Criteria |
|---|---|
| T1 | Tumour limited to one subsite of supraglottis, normal cord mobility |
| T2 | Invades mucosa of $\geq 2$ adjacent supraglottic subsites OR glottis OR region outside supraglottis (vallecula, medial wall of pyriform), without fixation |
| T3 | Limited to larynx with cord fixation OR invades postcricoid area, pre-epiglottic space, paraglottic space, or inner cortex of thyroid cartilage |
| T4a | Through thyroid cartilage OR invades beyond larynx (trachea, soft tissues of neck, strap muscles, thyroid, oesophagus) |
| T4b | Encases carotid OR invades mediastinum or prevertebral space |
T Staging (Larynx, Glottis)
| T Category | Criteria |
|---|---|
| T1a | Limited to one vocal fold, normal mobility |
| T1b | Involves both vocal folds, normal mobility |
| T2 | Extends to supraglottis or subglottis OR impaired cord mobility |
| T3 | Cord fixation OR paraglottic space OR inner thyroid cartilage erosion |
| T4a/T4b | As for supraglottis above |
Nodal Drainage
- Supraglottis: levels II, III, IVA, IVB; bilateral pattern common; pretracheal nodes also at risk
- Glottis: low risk unless T3/T4; levels IIA, III, IVA, IVB; paratracheal nodes for subglottic extension
- Subglottis: paratracheal, level VI
4. Hypopharynx
Anatomical Boundaries
Extends from the pharyngoepiglottic fold/vallecula to the inferior border of the cricoid cartilage; sits posterior and lateral to the larynx. Subsites: pyriform fossa (most common primary site), posterior pharyngeal wall, and postcricoid region.
Clinical Features
- Often silent until advanced; dysphagia and odynophagia are common presenting symptoms
- Referred otalgia
- High rate of occult cervical metastases (clinically node-positive in $\sim 70\%$ at presentation)
- Bilateral neck nodes are common due to midline proximity
- Distant metastases (lung, liver, bone) more frequent than for other subsites
T Staging (Hypopharynx)
| T Category | Criteria |
|---|---|
| T1 | Limited to one subsite, $\leq 2$ cm |
| T2 | Invades $> 1$ subsite or adjacent site, $2$-$4$ cm, without hemilarynx fixation |
| T3 | $> 4$ cm OR hemilarynx fixation OR oesophageal extension |
| T4a | Invades thyroid/cricoid cartilage, hyoid, thyroid gland, central compartment soft tissue, oesophagus |
| T4b | Encases carotid OR invades prevertebral fascia or mediastinum |
Nodal Drainage
Levels II, III, IV, V; paratracheal nodes (level VI) especially with postcricoid/subglottic extension. Bilateral involvement common.
5. Nasopharynx
Anatomical Boundaries
Extends from the skull base to the inferior surface of the soft palate. Bounded by the clivus and cervical spine posteriorly, nasal choanae anteriorly, and lateral walls containing the fossa of Rosenmüller and the Eustachian tube orifice.
Unique Features
- Predominantly EBV-driven; p16 plays no staging role here
- WHO histological classification:
- Type I: Keratinising SCC; not EBV-associated; sporadic; worst prognosis
- Type II: Non-keratinising differentiated SCC; EBV-associated
- Type III: Non-keratinising undifferentiated (lymphoepithelioma); EBV-associated; best response to radiotherapy
- Level V (posterior triangle) adenopathy in an adult should be considered NPC until proven otherwise
- Bilateral cervical metastases common at presentation
T Staging (Nasopharynx)
| T Category | Criteria |
|---|---|
| T1 | Confined to nasopharynx, or extends to oropharynx/nasal cavity without parapharyngeal involvement |
| T2 | Parapharyngeal extension and/or adjacent soft-tissue involvement (medial/lateral pterygoid, prevertebral muscles) |
| T3 | Skull base bony involvement, cervical vertebra, pterygoid structures, or paranasal sinuses |
| T4 | Intracranial extension, cranial nerve involvement, hypopharynx, orbit, parotid, or extensive lateral pterygoid muscle infiltration |
N Staging (Nasopharynx: distinct system)
| N Category | Criteria |
|---|---|
| N0 | No regional nodal metastasis |
| N1 | Unilateral cervical nodes AND/OR unilateral or bilateral retropharyngeal nodes, $\leq 6$ cm, above the caudal border of the cricoid |
| N2 | Bilateral cervical nodes, $\leq 6$ cm, above caudal cricoid |
| N3 | Nodes $> 6$ cm OR extension below the caudal border of the cricoid |
Shared Nodal (N) Staging for Oral Cavity, Oropharynx (HPV-negative), Larynx and Hypopharynx
| N Category | Criteria |
|---|---|
| N0 | No regional nodal metastasis |
| N1 | Single ipsilateral node $\leq 3$ cm, extranodal extension (ENE) negative |
| N2a | Single ipsilateral node $3$-$6$ cm, ENE negative |
| N2b | Multiple ipsilateral nodes, none $> 6$ cm, ENE negative |
| N2c | Bilateral or contralateral nodes, none $> 6$ cm, ENE negative |
| N3a | Node $> 6$ cm, ENE negative |
| N3b | Any node with clinical ENE positive |
Extranodal extension is a critical pathological adverse feature and an indication for adjuvant concurrent chemoradiotherapy (cisplatin-based) following surgery.
Clinical Assessment: The Systematic Workup
History
- Symptom duration, progression, and subsite-specific red flags (dysphonia, dysphagia, trismus, referred otalgia, epistaxis, nasal obstruction, stridor)
- Tobacco, alcohol, and HPV/sexual history; occupational exposures
- Prior head and neck irradiation
- Unintentional weight loss, constitutional symptoms
Physical Examination
Systematic examination must be performed before any imaging or biopsy:
- Inspection and palpation of all oral cavity and oropharyngeal mucosal subsites (remove dentures; bimanual palpation of tongue, floor of mouth)
- Fiberoptic nasolaryngoscopy: nasal cavity, nasopharynx, oropharynx, hypopharynx, larynx; assess cord mobility
- Neck: systematic palpation of all levels I-VI bilaterally; note size, number, fixity, and ENE signs (skin tethering, fixation to deep structures)
- Cranial nerve assessment: particularly CN V, VII, IX, X, XI, XII
- Thyroid and salivary gland palpation
Investigation Pathway
| Step | Investigation | Purpose |
|---|---|---|
| 1 | Fiberoptic endoscopy | Define primary; assess cord mobility |
| 2 | FNA of neck mass | Cytological diagnosis; avoid open biopsy pre-planning |
| 3 | MRI head/neck OR CT neck with contrast | Soft tissue extent, perineural spread, nodal assessment |
| 4 | CT chest (or PET-CT) | Distant metastasis, synchronous primary |
| 5 | PET-CT | Unknown primary; distant staging; post-treatment surveillance |
| 6 | Panendoscopy + biopsy under GA | Histological confirmation; synchronous primaries (3-5% rate); ipsilateral tonsillectomy for unknown primary |
| 7 | HPV/p16 testing | Mandatory for oropharyngeal SCC |
| 8 | EBV serology/EBER ISH | NPC diagnosis and monitoring |
| 9 | Formal audiogram | Pre-cisplatin baseline |
| 10 | MDT review | Treatment planning after full staging |
Panendoscopy includes direct laryngoscopy, oesophagoscopy, and bronchoscopy. For an unknown primary SCC of the neck (with no identifiable primary on imaging or endoscopy), ipsilateral (or bilateral, based on nodal laterality) tonsillectomy and directed biopsies of tongue base, nasopharynx, and pyriform fossae are performed. PET-CT prior to panendoscopy increases primary detection rates.
Multidisciplinary Team (MDT) Framework
All patients with HNSCC in Australia and New Zealand should be discussed at a formal MDT prior to treatment. The MDT typically comprises:
- Head and neck surgeon, radiation oncologist, medical oncologist
- Radiologist and nuclear medicine physician (imaging review)
- Pathologist (histology, HPV/EBV review)
- Speech-language pathologist, dietitian/nutritionist, dental oncologist, clinical nurse specialist
- Palliative care liaison where appropriate
MDT agreement on staging, resectability, functional reserve, and patient goals of care underpins treatment decisions.
Complications and Special Considerations
Airway Assessment and Planning
- Stridor, dyspnoea, or significant supraglottic/glottic disease requires urgent airway assessment
- Awake fibreoptic intubation is the technique of choice for anticipated difficult airways in HNSCC
- Preoperative anaesthetic consultation and surgical airway standby (surgical tracheostomy) must be planned for cases with severe glottic/subglottic compromise
- Elective tracheostomy may be required prior to definitive resection for large glottic or transglottic tumours
Synchronous Primaries
- The rate of synchronous second primary malignancy in HNSCC is approximately 3-5%; most commonly in the lung or oesophagus
- CT chest and panendoscopy are standard components of staging
Distant Metastasis Work-up
- Most common sites: lung $>$ liver $>$ bone
- Hypopharyngeal SCC has the highest rate of distant metastasis among the UADT primaries
- PET-CT has higher sensitivity than conventional imaging for distant disease
HPV-Positive Oropharyngeal SCC: Key Distinctions
- Staged with its own AJCC classification (HPV-positive oropharyngeal carcinoma, p16-positive)
- Better overall and disease-specific survival compared with HPV-negative disease
- Current clinical trials explore de-escalation of treatment intensity (lower radiation dose/volume, reduction of cisplatin) to reduce long-term toxicity while maintaining oncological outcomes
Extranodal Extension (ENE)
- Clinical ENE (skin involvement, nerve infiltration, vascular encasement) upstages to N3b
- Pathological ENE found at surgical resection is an absolute indication for adjuvant concurrent chemoradiotherapy
Management Principles by Stage
Stage I/II (Single Modality)
- Oral cavity: surgery preferred; allows DOI assessment and margin control
- Glottic larynx: radiotherapy or endoscopic laser excision preserve voice
- Oropharynx: either surgery (transoral robotic/laser) or radiotherapy depending on site and function
- NPC: primary radiotherapy (chemotherapy added for $\geq$ T2 or N1)
Stage III/IVA (Multimodality)
- Oral cavity and larynx resectable disease: surgery + adjuvant radiotherapy (with concurrent cisplatin if positive margins or pathological ENE)
- Larynx/hypopharynx: organ-preservation protocols (concurrent cisplatin-based CRT); total laryngectomy reserved for CRT failure or functionally non-viable larynx
- Oropharynx: definitive concurrent CRT is standard for most (particularly HPV-positive)
- NPC: concurrent cisplatin + radiotherapy with adjuvant chemotherapy for N2/N3
Stage IVB/IVC (Unresectable / Distant Metastasis)
- Definitive CRT (platinum-based) for locoregionally unresectable disease
- Palliative systemic therapy: platinum/5-FU/cetuximab (or pembrolizumab-based regimens per current evidence) for recurrent/metastatic disease
Summary: Subsite-Specific Staging and Clinical Pearls
| Subsite | Key T Feature | Key N Feature | Primary Nodal Levels | Special Consideration |
|---|---|---|---|---|
| Oral cavity | Depth of invasion determines T1 vs T2 | Standard AJCC N | I, II, III | DOI drives elective neck dissection decision |
| Oropharynx | Size-based; epiglottis extension T3 | Separate system for HPV+ | II, III, IV; retropharyngeal | p16/HPV mandatory; de-escalation trials |
| Larynx (supraglottic) | Cord fixation = T3 | Standard AJCC N | II, III, IV; pretracheal bilateral | Bilateral drainage; organ preservation |
| Larynx (glottic) | Cord mobility is cardinal feature | Low-risk N until T3+ | II, III, paratracheal | Early dysphonia facilitates early diagnosis |
| Hypopharynx | Hemilarynx fixation = T3 | Standard AJCC N; high N+ rate | II, III, IV, VI | Highest distant metastasis rate; worst prognosis |
| Nasopharynx | Parapharyngeal = T2 | Distinct N system; ENE less relevant | Retropharyngeal, II-V bilateral | EBV-driven; level V node is cardinal sign; RT primary modality |
Perioperative and Long-term Considerations
- Dental review before radiotherapy to extract compromised teeth and reduce osteoradionecrosis risk
- Nutritional optimisation: nasogastric or percutaneous gastrostomy feeding for patients with anticipated severe mucositis or resection-related dysphagia
- Audiology baseline before cisplatin therapy; repeat during and after
- Speech and swallowing assessment both pre-treatment (baseline) and post-treatment
- Thyroid function monitoring after neck irradiation (hypothyroidism in 20-40% at 5 years)
- Post-treatment surveillance: clinical examination and endoscopy every 1-3 months for year 1, extending to 6-monthly in year 3-5; imaging guided by symptoms or clinical suspicion; EBV viral load monitoring for NPC
- Smoking cessation improves radiotherapy efficacy and reduces second primary risk; formal cessation support is a standard MDT recommendation