Salivary Gland Tumours

DEFINITION
Tumours of major (parotid, submandibular, sublingual) or minor (scattered submucosal) salivary glands, benign and malignant.

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EPIDEMIOLOGY

As per lesion.
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AETIOLOGY

Parotid
Commonest site.
Consider discrete mass vs diffuse swelling

Discrete mass
Any mass in region of parotid
- ie. (below zygomatic arch, behind anterior border of masseter, above upper neck, anterior to mastoid)
--> should be considered a parotid mass until proven otherwise.
80% tumours occur in parotid
- and 80% of these are benign

Parotid benign tumours

1. Pleomorphic adenoma
(Variable mix of glands and elements histologically, arise from myoepithelial cells).
65-75% of parotid tumours
Slow growing, firm, smooth, usually asymptomatic.
Peaks 5th decade, slightly F>M, but can occur at any age.
Malignant transformation uncommon
- rarely reported in those present <10y
- bossellations may develop
--> but rapid growth and facial nerve involvement are hallmarks of malignant change.

2. Adenolymphoma (Warthin's tumour)
Much less common than pleomorphic but 2nd most common benign parotid tumour
(Dense lymphocytic infiltration; origin uncertain)
- 10% are bilateral.
~5-10% of parotid tumours
Peak in 5th decade
Associated with smoking
Benign, softer tumour, M>F
Often in inferior pole of parotid
Highly unlikely to become malignant
Histologically big pink cells wtih centrally placed pyknotic nuclei.

3. Rare
Monomorphic adenoma and oncocytoma.
Pathological finding on diagnosis after excision; often unclear FNA.

Parotid malignancy
15-20% of parotid tumours

Secondary
Most common = metastatic SCC in intraparotid lymph nodes
Rapid growth causes tumour necrosis, usually showing as a with cystic lesion in parotid

Primary
1. Mucoepidermoid carcinoma
Most common primary malignancy of parotid
Childhood onwards, peaks 5-6th decades
- Most (75%) are low grade, slow-growing parotid mass.
- High-grade tumours grow fast and have a poorer prognosis.
Cystic; tan yellow
Lymph node mets uncommon.
Resemble SCC histologically, but show mucous staining.

2. Adenoid cystic carcinoma
2nd most common.
Slow growing, asymptomatic masses
Early perineural spread; may present with facial n. weakness
Good 5 year survival but...
Propensity for late recurrence, often to bone, lung, even up to 20y later.

3. Acinic cell tumour
Low grade malignancy from reservoir cells of terminal ducts
F>M in 5th decade
Benign early course; 20y survival 50%.

4. Malignant pleomorphic adenoma
Can arise de-novo or in a pre-existing pleomorphic adenoma
Usually aggressive

5. Adenocarcinoma
Otherwise unspecified.  May arise in the parotid and is aggressive.

Submandibular
Relatively uncommon
But more likely to be malignant (40%)

Pleomorphic adenoma
Slowly growing asymptomatic lump as in parotid
Differentiation from submandibular nodes by aspiration cytology.
Total gland excision
Malignant spread may require sacrifice of lingual and hypoglossal nerves and radiotherapy

Adenoid cystic most common submandibular gland.

Sublingual
Rare.
60% Malignant.


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BIOLOGICAL BEHAVIOUR

Anatomy/Physiology

Parotid
Serous
Intimately involved with facial n; enters posteriomedially as a single trunk, then divides and exits as 5 branches.
- n. divides gland into superficial and deep
Superficial = covered by skin, platysma (in part) and parotid fascia;
Deep = lies in parapharyngeal space, through which passes posterior facial vein and external carotid artery.
Drains to parotid duct, which crosses the masseter and enters buccal cavity opposite upper 2nd molar.

Submandibular
Mixed
Close to inner aspect of mandible, on mylohyoid muscle.
Superficial = covered by skin, platysma and deep cervical fascia
- crossed at upper border by mandibular branch of facial nerve on way to supply depressor anguli oris
- posterior aspect wrapped around posterior border of mylohyoid
Deep = passes forward, deep to the mylohyoid lying on hypoglossus.
Duct drains from deep lobe, running long course in floor of mouth to open at papilla in anterior floor of mouth, lateral to lingual frenulum
Lingual n. closely related to deep lobe and duct; at risk.
Deep lobe related to mylohyoid (inferolaterally) and supramedially is covered by oral mucosa in floor of mouth
--> easily examined by bimanual examination.
--> and differentiated from lymph node swellings.

Sublingual
Mucous
Submucosally on anterior floor of mouth, supported by mylohyoid m's.
Drain by multiple ducts onto floor of mouth along sublingual folds


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MANIFESTATIONS

Symptoms

Slow growing lump ~benign
Fast ~malignant

Signs
Perform intra-oral and manual exam.
Note site, size, shape surface texture, tenderness, fixation, involvement of surrounding structures, lymph nodes
Deep parotid lesions may be detected as a diffuse bulge in the roof of the soft palate or tonsillar fossa.

Always assess facial n. function with parotid lesions
Test tongue sensation if submandibular problems.
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INVESTIGATIONS

CT
To clarify anatomical relationships

MRI
If suspicion of cranial N. involvement

FNA
Yes. No associated risk of seeding.
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MANAGEMENT

Pleomorphic adenoma

Given:
i) Relentless growth pattern
ii) chance of malignant change
iii) inability to differentiate this tumour from slow-growing malignant tumours
--> Surgically excise all parotid tumours.

Establish that the mass is mobile within the parotid
Cytology may help plan urgency and timing of surgery
CT only necessary when malignancy suspected.

Excise lesion with intact capsule and preservation of facial nerve.
- incomplete excision or capsular rupture predisposes to local recurrence
--> may be multinodular and exceedingly difficult to eradicate.
Complete excision associated with <2% recurrence rate

Superficial parotidectomy
Identify the main trunk of the facial nerve
- then trace it through the gland while tumour with surrounding parotid tissue is excised.

Deep tumours
Superficial gland excised first.
Then facial nerve and branches fully mobilised to allow deep lobe removal (either between branches or below facial nerve).

Risk of nerve damage is low, but some degree of temporary weakness due to neuropraxia is not uncommon.

Adenolymphoma (Warthin's Tumour)
Cytologic picture is diagnostic
Parotidectomy unless elderly and frail.

Parotid Secondary SCC
CT
Surgical excision
Usually with neck dissection
Post-operative radiotherapy

Malignant Parotid Tumours
Based on biological and histological features.

1. Surgical excision
Low grade --> superficial, e.g. low grade mucoepidermoid
Total with sparing of the nerve if aggressive.
Usually curative for slow-growing discrete low-grade lesions
With sparing of facial nerve.

2. Radiotherapy
After low grade if margin involved.
Use with pleomorphic controversial
Following surgery, for those with more aggressive histological features
Also for recurrence is primary modality.

3. Lymph node dissection
Us. only if clinical or radiological evidence of involvement.

What if facial nerve involvement?
Radical surgery with facial nerve sacrifice
Followed by radiotherapy
Primary nerve grafting using the sural nerve is performed in some centers.




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Jerome Notes


Neoplastic

In adults »80% parotid, 80% benign, 80% pleomorphic adeonoma

45% of tumours in submandibular gland are malignant

50% of tumours in minor salivary gland are malignant and 50% adenoid cystic carcinoma

60% of salivary neoplasms in children are malignant

 

Epidemiology

Sex

· Benign F>M

· Malignant M=F

Distribution overall

· Parotid 80%

· Submandibular 15%

· Sublingual 5%

Incidence malignancies

· Parotid 20%

· Submandibular 40%

· Sublingual 50%

Pathology

Benign epithelial

Pleomorphic adenoma

· Commonest (70%)

· Parotid and submandibular

· 10% occur in deep lobe and should be treated with conservative total parotidectomy and preservation of the facial nerve.

· Lesions in superficial lobe are treated by superficial parotideomy; lesions in submandibular gland are treated by gland exision.

· Enucleation produces a 40% risk of recurrence.

· M=F

· Peak 5th decade

· Slow growing

· Smooth lobulated mas

· Arise from myoepithelial and intercalated duct cells

· Incomplete capsule, satellite nodules, pseudopod

· Epithelia and mesenchymal components

· Malignant change 2-10% (10-20yrs)

· FNA »90% accurate

Monomorphic adenoma

· Proliferation of epithelial components in the absence of mesenchymal cells

· Includes sebaceous lymphadenoma, basal cell adenoma, myoepithelioma

Adenolymphoma (Warthin’s) papillary cystadenoma lyphomatosum

· Second most common (»14%)

· Exclusively parotid

· Peak 55yrs; closely associated with smoking

· bilateral (10%)

— 70% of bilateral tumours

· 90% males

· Soft or fluctuant

· Can be fixed to skin

· Cyst like spaces , double layer epithelium, surrounding lymphocytic infiltartion

· Malignant change v. rare

Oxyphilic adenoma (Oncocytoma)

· Solitary, encapsulated, slow growing

· Parotid

· Bilateral

· Women

· 6th decade

· LNM 10%

· 5yrs 50%

Benign Non epithelial tumours

· Rare

· Haemangiomas, lymphangiomas, lipomas

 

Malignant epithelial tumours

Mucoepidermoid

· Commonest Ca (12% of salivary gland tumours)

— Commonest salivary gland tumour in children

· Parotid > other salivary glands

· 20-60yrs

— peak 5th decade

· F³M

· Derived from squamous and mucus secreting cells

· Firm ill defined

· High grade

— ­aggressive growth, more solid, 5yrs 40%

· Low grade

— More cystic, 5yrs 90%

· LNM 40%

· Recurrence rate 30%

· Mets to brain, skin, bone, lung

Adenocystic

· Most common ca in submandibular

— However, most occur in parotid

· M=F

· 6th decade

· slow growing

· Nerve involvement

— Facial paralysis and pain

· Skin ulceration

· Bony involvement early

— Along marrow cavities

· Cribriform and tubular patern

— Can diagnose on FNA

— Perineural invasion frequent (60%)

· Prognosis related to completeness of excision

· 10yrs 70%, 20 yrs 20%

Malignant mixed tumour

· Arises in pleomorphic adenomas

— <10%

· Poor prognosis

— High incidence of mets

— High recurrence

— 40% 5yrs

Acinic

· 3-4% of salivary gland tumours

· predominantly parotid

· 5th decade, but also teenagers and children

· single, encapsulated, satellite lesions

· Histology

— Serous acinar cells, granular basophilic cytoplasm

· LNM 10%

· 5yrs >50%

Adenocarcinoma

· Many types

— Mucinous, ductal, clear cell

· Firm, solitary ± mucucs ± papillary cells

· LNM 25%, 5yr 65%

Squamous

· Metastatic ‘till proved otherwise

· M>>F

· Submandibular gland

· 5th decade

· Variable growth

· Commonly fixed

· LNM common

· 5yrs 50%

Undifferentiated

· Solitary firm rapid growing

· Usually parotid

· 7th –8th decade

· Histology

— Anaplastic invasion, spherical or spindle cells

— LNM 25%

— 5yrs 35%

Ductal

· Minor glands

· Mostly palate

· Low grade malignancy

· 30% recurrence

Non epithelial tumours

· V. rare

· Sarcoma, lymphoma (invade from LN, or arise in gland in Sjφgren’s – extra-nodal B cell NHL)

Metastatic

· Melanoma

· SCC

Staging

TNM

· T

T1 £ 2 cm

T2 > 2 cm £ 4 cm

T3 extraparenchymal extension without seventh nerve involvement and/or > 4 cm

T4a invades skin, mandible, facial nerve or ear canal

T4b invades base of skull, pterygoid plates or encases carotid artery

· N

N1 single ipsilateral lymph node, £ 3 cm

N2 single, bilateral or contralateral lymph nodes £ 6 cm

a single ipsilateral > 3 cm £ 6 cm

b multiple ipsilateral £ 6 cm

c bilateral or contralateral £ 6 cm

N3 > 6 cm

Stage

· I T1-2, N0, M0

· II T3, N0, M0

· III T1-2, N1, M0

· IV T4, N0, M0 T3-4, N1, M0 Any T, N2-3, M0 Any T, Any N, M1

Clinical

Malignant

· discrete masses 95%

· Pain 10-25%

— Rare in benign tumours

· Facial nerve dysfunction 10-25%

· Formication 17%

— Paraesthesia akin to ants crawling on skin

· Ulceration 10%

Ix

· Hx, Ex

— Bimanual

— Cranial nerve function: facial nerve weakness is usually indicative of malignancy. 80% of patients with facial nerve weakness have lymph node metastasis at the time of diagnosis.

—   Ausculatation over orbit, cheek, neck

—   Full ENT examination including oral cavity and flexible endoscopy to rule out that the parotid malignancy is a metastasis from another site.

—   Examine scalp

· Ix

— FNA often under US guidance: 95% sensitivity – first investigation of choice for any patient with salivary gland neoplasm

— MRI / CT – can help differentiate whether mass is in superficial or deep lobe of parotid – which helps in surgical planning. Imaging is a poor means of differentiating benign and malignant disease

— CXR

Rx

Principles of surgical treatment of salivary gland tumours

Malignant tumours of the parotid warrant total parotidecomy (with exception of low risk T1/T2 tumours (well mucoepidermoid and acinic cell)

Facial nerve should be sacrificed only when there is involvement or facial nerve paralysis

High grade tumours should undergo elective neck dissection for N0 disease or modified radical dissection for palpable adenopathy

Post-op RT is indicated if:

—   high-grade neoplasms

—   Extra-parenchymal spread of cancer

—   Involvement of skin, nerve or bone

—   Positive neck nodes

—   close or involved margins

—   Recurrent disease

 

· Group I: T1 or T2 N0M0 low grade acinic or mucoepidermoid carcinoma: superficial parotidectomy with facial nerve preservation.

· Group II: T1 or T2 high grade lesions (high grade mucoepidermoid, adeno or malignant mixed): Total parotidectomy with preservation of facial nerve if not involved, resection of facial nerve if involved (with immediate grafting from sural nerve), neck dissection and post-op XRT.

· Group III: T3 or N1+: radical surgical excision to include deep lobe if involved. Facial nerve excision and grafting if involved. T3N0: modified radical neck dissection, T3N+radical neck dissection. All patients receive post op RT

Group IV: T4 – radical parotidecomy to include involved surrounding tissue (buccal fat, skin, ear canal, mastoid), primary reconstruction including facial nerve. Post-op XRT.  

· Resect facial nerve and/or branches if involved by tumour

— repair can be done simultaneously once frozen section has shown resected nerve margins to be clear

· evidence that postop XRT augments surgical resection

—   high-grade neoplasms

—   Extra-parenchymal spread of cancer

—   Involvement of skin, nerve or bone

—   Positive neck nodes

— close or involved margins

Only for low grade T1/T2 tumour with clear resection margins or pleomorphic adenoma completely resected is XRT not required.

· Fast neutron beam radiation improves DFS & OS in patients with unresectable tumors or for those with recurrent neoplasms.

— Ltd facilities

· Chemotherapy remains under evaluation

· Neck dissection

— mucoepidermoid

— SCC

— Palpable nodes