Tumours of the Oral Cavity

Anatomy of Oral Cavity Tumours

Borders

• Anterior: wet-dry border of the lips
• Posterosuperior: hard-soft palate junction
• Posteroinferior: tongue's circumvallate papillae, tonsil's anterior pillars (created by the palatoglossus muscle)

Contents of the Oral Cavity

There are 7 key anatomical structures in the oral cavity. They can be remembered by the mnemonic FRAMPAL, which is explained below.

• Floor of the mouth: bounded by inferior alveolar ridges and tongue.
• Retromolar trigone: mucosa over the anterior aspect of ascending ramus formed by oropharynx, nasopharynx, buccinator, floor of mouth and parapharyngeal space.  
• Alveolar ridges: superior and inferior.
• Mucosa (Buccal): inner cheeks & lips anterior to pterygomandibular raphe.
• Palate (Hard): between the superior alveolar ridge and soft palate junction.
• Anterior 2/3 of the tongue: anterior to circumvallate papillae.
• Lips: inner aspect.

Clinical Picture of Oral Cavity Tumours

History

Patients' symptoms can be a nonhealing ulcer or mass growth. In more advanced stages, a patient may have local and regional symptoms such as:

• Teeth: unexplained tooth loss.  
• Trismus: tonic contraction of the muscles of mastication reducing mouth opening. This can be due to oedema, pain, invasion of muscles, or radiotherapy-induced fibrosis.
• Referred otalgia: convergence theory suggests there are common sensory pathways between ear and cranial nerves that result in patients being unable to correctly pinpoint the location of pathology¹ . It is linked to innervation by cranial nerve IV.
• Nodes: usually submandibular (Level I), upper/middle jugular (Level II, III)

Risk Factors

Patients with oral cavity tumours may also have the following risk factors:

• Toxins: tobacco, alcohol, betel nut (causes fibrosis)
• Infections: oral HPV-16 infection (different staging system due to better prognosis), AIDS (hairy leukoplakia)
• Patient Status: poor nutrition, immunosuppressed or immunocompromised
• Genetics: Fanconi's Anaemia (recessive), Li-Fraumeni syndrome (p53 gene)
• Pre-malignant lesions: leukoplakia, erythroplakia

Radiological Findings

MRI is the modality of choice for oropharyngeal tumours. T1-weighted images show fat as white and water as black. The opposite is true for T2.  

• CT Neck/Chest with Contrast: gold standard, bone invasion
• PET/CT: metabolic FDG-avidity for staging and useful if dental artefact.
• MRI: good for soft-tissue definition, assess nerve involvement.
• Pandendoscopy: looking for synchronous tumours.

Premalignant Lesions

Leukoplakia

• A white patch that cannot be easily removed or scraped off.
• It cannot be explained by another condition, therefore a diagnosis of exclusion.
• A biopsy may show non-dysplastic or dysplastic epithelium (~25%)
• Dysplastic leukoplakia should be excised due to risk of malignant transformation (~20%).

Erythroplakia

• A red patch that is soft with a velvety texture.
• Higher risk of dysplasia and malignancy on biopsy compared to leukoplakia.
• Hairy leukoplakia can be seem in immunosuppressed or compromised patients, such as HIV/AIDS.
• It is also a diagnosis of exclusion and should be exicsed.

Other pathologies to consider are:

• Actinic Cheilitis (Sailor's Lip)
• Proliferative Verrucous Leukoplakia
• Tobacco Pouch Keratosis
• Lichen Planus

Types of Oral Cavity Tumours

Squamous Cell Carcinoma

Squamous cell carcinoma of the head and neck arises from epithelial cells and occurs in the oral cavity, pharynx and larynx. This is the most common pathology in the oral cavity.

It should be distinguished from cutaneous squamous cell carcinoma.

Other Pathologies

• Salivary gland: mucoepidermoid, adenocarcinoma, adenoid cystic carcinoma
• Mucosal melanomas: rare but usually present as locally aggressive tumours, mainly of the hard palate and gingiva.
• Sarcomas: including osteosarcoma of the mandible or maxilla
• Odontogenic tumours: such as ameloblastoma
• Haematological: including lymphoma and leukaemia.
• Metastasis to the Mouth or Cancer of Unkown Primary.

Treatment of Oral Cavity Tumours

Overview of Treatment Options

After a discussion at a multidisciplinary meeting, treatment options for the oral cavity tumours depend on the tumour characteristics, the extent of disease and patient status.

Treatment options include:

• Surgical Resection (5-10mm margins) ± Reconstruction ± Neck Dissection
• Chemotherapy
• Radiotherapy: nodal disease, T2, palliative or no surgical option.
• Multimodal: surgery with adjuvant chemoradiotherapy
• Immunotherapy: experimental

Surgery

Generally speaking, oral cavity tumours require surgical Resection (5-10mm margins) ± reconstruction ± neck dissection. There are different approaches to an oral cavity tumour, which can include:

• Transoral: consider if tumour is <T2.
• Lip split: midline then extend incision around aesthetic unit of chin.
• Mandibular split: Paramedian/parasymphysis on the side of the tumour
• Visor approach: divide mental nerves and retract jaw down
• Pull through: apron incision from midline to 3cm above the mastoid, which allows you to retract neck superiorly and detach the insertion of the tongue muscles by doing osteotomy of bottom of mandible.

Neck dissections should be considered for T2 disease or those with clinical nodal disease. This is an ongoing debate. The type of dissection can be:

• Supraomohyoid (I-III) for N0 and N1 tumours of the oral cavity
• Modified neck dissection for palpable metastases
• Radial neck dissection if involvement of nerve, vein or muscle

Reconstruction

The goals of reconstruction are to recreate a lining to the oral cavity, maintain oral competence, and enable swallowing and speech. The cosmetic outcome should also be considered.

To achieve these goals, different options can be provided from local, regional or distant flaps. This depends on the size and location of the defect and can be assisted by virtual surgical planning/computer-animated design.

Examples include:

• Local: mucosal, facial artery musculomucosal.  
• Regional: pectoralis major, deltopectoral, parascapular
• Distant: radial artery forearm, anterolateral thigh, rectus abdominis

Reconstructive with vascularised healthy tissue assists the adjuvant radiotherapy treatment if needed.

Radiotherapy

Radiotherapy should be considered for oral cavity primary tumours. In particular, if these tumours are:

• T3 or T4 lesions
• Close or positive surgical margins
• Perineural or lymphovascular invasion
• Extracapsular spread.  

Oral Cavity Cancer Staging

Oral cavity carcinoma staging is outlined in the AJCC 8th Edition Staging Guidelines². This staging criterion refers to squamous cell carcinomas as well as less common epithelial and minor salivary gland cancers.

Primary tumour (T)

• Tx: primary tumour cannot be assessed
• Tis: carcinoma in situ (dysplastic lesions with intact basement membrane)
• T1: ≤2 cm + DOI ≤5 mm
• T2: ≤2 cm + DOI 5-10 mm, or 2-4 cm + DOI ≤10 mm
• T3: >4cm or any size + DOI 10-20mm
• T4a: DOI>20 mm, or invade mandible, inferior alveolar nerve, maxilla bone or sinus, skin.
• T4b: invade masticator space, pterygoid plates, skull base, and carotid artery. Superficial erosion alone of bone/tooth is not T4 disease.

Regional lymph node (N)

Regional nodal status can be clinical (no lymph node dissection) and pathological (lymph node dissection). It is similar to most other head and neck cancers (HPV-negative oropharyngeal, hypopharynx, larynx).

Clinical nodal status (cN)

Clinical nodal status arises from examination, imaging, and fine-needle aspiration.

It depends on the number, size, location and extranodal extension (ENE status).

• Nx: nodes cannot be assessed
• N0: no regional node metastases
• N1: single ipsilateral node ≤3 cm & ENE^-
• N2a: ipsilateral node ≤3 cm & ENE⁺ or ipsilateral node 3-6 cm & ENE^-
• N2b: multiple ipsilateral nodes ≤6 cm & ENE^-
• N2c: bilateral or contralateral nodes ≤6 cm & ENE^-
• N3a: single node >6 cm & ENE^-
• N3b: single node with clinically overt ENE⁺, or multiple nodes and ENE⁺, single contralateral nodes and ENE⁺, or single node >3cm and ENE⁺.

It can be difficult to remember, so here are some tips!

• Multiple nodes: N2b is the lowest nodal status.
• Contralateral or bilateral: N2c is the lowest nodal status.
• Node >6cm: N3a is the lowest nodal status.
• If ENE⁺: N2a if ≤3 cm or N3b if >3cm.
• If N3b: the node must be ENE⁺.

Distant metastases (M)

• cM0: no evidence of metastases
• cM1: distant metastasis
• pM1: distant metastasis, microscopically confirmed

Stage groups

The prognostic stage groups are defined the same as for most other cancers of the head and neck:

• Stage 0: Tis, N0, M0
• Stage I: T1, N0, M0
• Stage II: T2, N0, M0
• Stage III: T3, N0, M0 or [T1, T2, T3], N1, M0
• Stage IVA: T4a, [N0, N1], M0 or [T1, T2, T3, T4a], N2, M0
• Stage IVB: [Any T], N3, M0 or T4b, [Any N], M0
• Stage IVC: [Any T], [Any N], M1

Flashcards