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Salivary gland tumours

Section: Head and neck Curriculum: Curriculum, page 42

Incidence

  • Larger salivary glands more likely to have benign pathology
  • Smaller glands get, higher the malignant incidence
    • Parotid - 20%
    • Submandibular - 50%
    • Sublingual - 80%

Classification

  • (Summary of WHO 2017 classification)
  • Benign
  • Malignant
    • Mucoepidermoid carcinoma
    • Adenoid cystic carcinoma
    • Carcinoma ex pleomorphic adenoma
  • Secondary
    • SCC
    • Melanoma
    • Lymphoma

Risk Factors

  • Radiation exposure
  • Viral infection - HPV, EBV, HIV
  • Environmental exposure - rubber manufacturing, hair dresser, nickel compounds
  • Smoking (Warthins Tumour)

Clinical

Local

  • Major gland
    • Painless mass/swelling
    • Facial nerve involvement suggests malignancy
  • Minor gland
    • Painless submucosal mass or mucosal ulceration
      • Palate, lips, buccal mucosa
      • Looks like SCC
    • Location and size driven
      • Nasal obstruction and congestion
      • Visual change
      • Trismus
      • Nasopharynx - invasion of skull base with CN involvement

Regional

  • Regional LN mets dependent on which gland is involved
  • Parotid - level 2
  • Submandibular - level 1
  • Sublingual - level 1
  • Minors - retropharyngeal

Distant metastasis

  • Lung, bone and liver usual spots
  • Adenoid cystic carcinoma can have distant mets even 20yrs after tx

Investigations

  • Helps to determine if benign vs malignant, location in relation to the gland, local invasion and extent
  • Imaging
    • Goals of imaging
      • Confirm dx
      • Location
      • TNM staging
    • USS
      • Good for 3 big glands and can guide FNA/core
    • CT
      • Bony involvement, distant mets
    • MRI
      • Sublingual location (high malignancy risk)
      • Soft tissue invasion
      • PNI
      • Intracranial extension
  • Biopsy - FNA or core
    • FNA 80% sens and spec, lower risk
    • Core 100% sens and spec, higher risk
    • All benign’s cardinal feature
      • Circumscribed growth
      • Absence of infiltrative growth pattern

Stage

TNM AJCC 8th Staging Salivary Gland Tumours

T1<2cm, no extraparenchymal invasion (clinical/MACROscopic)
T22-4cm , no extraparenchymal invasion
T3>4cm AND/OR 

extraparenchymal invasion
T4aModerately advanced

Invades skin, mandible, ear canal and/or facial nerve
T4bVery advanced

Invades skull base and/or pterygoid plates and/orencases carotid artery
N11x ipsilateral LN, 3cm or less, no ENE (ExtraNodal Extension)
N2a1x ipsilateral LN, 3-6cm, no ENE
N2b>1 ipsilateral LN, all <6cm, no ENE
N2c>1 bilateral/contralateral LN, al <6cm, no ENE
N3aAny >6cm, no ENE
N3bAny ENE +
M1Distant mets

Management

Overview

  • Benign
    • Complete excision for histology or if symptomatic
    • Consider surveillance if unclear or asymptomatic
  • Malignant
    • Excision with clear margins +/ RTx +/- nec dissection

Principles

  • Excise tumour with clear margins
  • Preserve facial nerve function if possible
  • Reduce risk of complications
  • Reduce risk of local recurrence
  • Options
    • Surgery
    • Radiation

Surgery

Parotid Gland

  • Superficial parotidectomy
    • For benign tumours
    • For malignant tumours that are
      • Low grade
      • High grade and peripheral
  • Total parotidectomy
    • High grade central/deep tumours
    • Wide resection
  • T4 tumours may need resection of
    • Bone - mandible, zygoma, temporal
    • Skin
    • Soft tissue/muscle
    • Nerve if involved
      • Nerve reconstruction or tx of facial droop
      • Nerve interposition graft

Submandibular Gland

  • Sialoadenectomy
  • Considerations
    • Facial artery and vein
    • MMN (CN7)
    • CN12 and lingual N
    • Submandibular duct
  • Approach
    • Transcervical → STANDARD FOR MALIGNANCY
    • Intraoral
    • Endoscopic
  • Malignant resection
    • En bloc with affected skin, soft tissue
    • Aforementioned nerves are preserved unless ENCASED

Sublingual Gland

  • Ipsilateral submandibular gland should also be resected
  • Even for small tumours
  • Due to duct involvement

Minor Salivary Gland

  • Surgical resection
  • Post op RTX as per same guidelines as SCC

Neck Dissection

  • Clinically positive pre op
    • If having surgery → do a neck dissection - level 2+3 definitely
    • Level 1,4 and 5 when indicated
    • Then adjuvant RTX
    • If having definitive RTX - thats it → NO NECK DISSECTION
  • Clinically negative - RTX and neck dissection equivalent
    • If having surgery for parotid → elective neck dissection if has high risk features
      • Locally advanced
      • High grade pathology
      • Facial nerve involvement
    • Elective neck dissection if cancer is sublingual or minor salivary gland
  • Summary of knowledge for salivary gland tumour neck dissections
    • Clinically positive
      • Neck dissection (level 2+3 +/- 1,4 and 5) if doing surgery anyways
    • RTX if definitively RTX treatment
    • Clinically negative
      • Elective neck dissection if
        • High risk and operating anyway
          • Locally advanced, high grade or facial nerve involved
    • Sublingual/minor salivary gland tumour
    • NOTE RADICAL = 1-5 + IJV, SCM and CN11

Radiation

  • Goal
    • Reduce locoregional recurrence
  • Dose
    • 60Gy 2Gy/fraction - tumour bed and LN
  • Indications
    • Adjuvant
      • High grade
      • Locally advanced
        • T3
        • Large >4cm
        • Skin/nerve/bone/soft tissue invasion
      • Located where wide resection not feasible e.g. nasopharynx
      • Adenoid cystic carcinoma
      • All non-parotid tumours
    • Definitive
      • Unresectable
      • Not fit for surgery

Neck Levels

I - submental and submandibular Ia - submental - anteromedial to ant belly digastric Ib - submandibular - posterolateral to ant belly digastric II - Upper IJ chain (deep cervical) IIa - anterior to IJV IIb - posterior to IJV III - Middle IJ chain (deep cervical) Note I, II and III are all anterior triangle and above hyoid bone IV - Lower IJ chain (deep cervical) V - Posterior triangle VI - Central (anterior compartment) VII - inominates to the jugular notch

Prognosis

  • Poor prognostic features from malignant salivary tumours
    • Demography/lifestyle - older, male, smoker
    • Pre-op facial nerve involvement
    • Positive LN
    • High grade, PNI, positive margins

Types

Benign

Pleomorphic Adenoma

Definition

  • Benign salivary gland tumour

Epidemiology

  • Rare <1%
  • F>M 2:1
  • Age 30-60
  • Most common salivary gland tumour
  • Most commonly affects parotid gland

Location

  • Mainly parotid 80% but can be in any other
    • Majority are superficial parotid
  • Malignancy risk
    • Low at 2-5%
    • Carcinoma ex pleomorphic adenoma
    • Can be within them therefore all should be excised

Risk Factors

  • Previous head and neck irradiation
  • Exposure - rubber, nickel

Histology

  • Proliferation of
    • Epithelial cells
    • Myoepithelial cells
    • Stromal/mesenchymal cells
  • Pseudopod extensions
    • Don’t enucleate - risk of recurrence higher
  • Benign
    • Circumscribed growth pattern without infiltration

Clinical

  • Slow growing painless mass

Investigations

  • USS - hypoechoic, lobulated, posterior acoustic enhancement
  • CT - lobulated mass, homogenous
  • MRI - soft tissue involvement
  • USG - FNA or core biopsy for histology

Management

  • Surgery
    • Parotid - Superficial Parotidectomy facial nerve preservation
      • Enucleation has high recurrence rates up to 50%
      • Total parotidectomy does NOT reduce recurrence risk
        • BUT does increase risk of nerve damage
    • Submandibular - gland excision
  • Radiation
    • Indications
      • Positive margins (should really re-resect if possible)
      • Multiple recurrence
      • Inoperable primary or recurrence
  • Recurrence
    • Why does it occur?
      • Pseudopod formation
      • Incomplete capsule
      • Close proximity to facial nerve and branches
  • Complications of Parotidectomy
    • 5 F’s
      • Frey’s syndrome - prevention → thick flaps (SCM), post op RTX, botox
      • Formication
      • Flap necrosis
      • Fistula
      • Facial N injury

Spiel on pleomorphic adenoma

  • Most common benign salivary gland tumour
  • Typified by epithelial, myoepithelial and stromal proliferation
  • Mainly parotid (80%)
  • RFs same as other tumours - environmental exposure - rubber, nickel compounds, hairdresser. prior radiation, viral - HIV, HPV, EBV
  • Important due to small risk of harboring carcinoma ex pleomorphic adenoma 5%
  • Painless neck lump
  • Diagnosed with CT/MRI and biopsy (FNA or core)
  • Mx is with superficial parotidectomy with facial nerve preservation
  • Risks of surgery include Freys, formication, fistula and facial nerve injury
  • Recurrence rate low with above, higher with enucleation
  • Can be given RTX for recurrence but prefer surgery if possible
  • Risk increases with recurrent surgery

Warthins Tumour

Definition

  • Benign salivary gland tumour

Epidemiology

  • Rare <1%
  • 2nd most common benign parotid gland tumour
  • M>F

Risk Factor

  • SMOKING (only salivary gland tumour associated to smoking)
  • Others
    • Radiation
    • EBV

Location

  • Parotid (almost exclusively)

Features

  • Commonly cystic and bilateral

Pathology

  • Macro
    • Well circumscribed mass
    • Solid and cystic components
  • Micro
    • Bilayered oncocytic epithelium
    • Cyst formation
    • Lymphoid stroma

Clinical

  • Painless lump near angle of mandible

Investigations

  • Assess both sides - bilaterality and multiple
  • USS - well defined mass, anechoic areas, post acoustic shadowin
  • CT - bony involvement
  • MRI - soft tissue involvement, encapsulated, hypo T1
  • Biopsy - FNA or core

Management

  • Usually superficial parotidectomy
  • Surveillance if biopsy proven and not changing, asymptomatic
    • Low recurrence rate and minimal malignant potential

Spiel on Warthin’s tumour

  • 2nd most common benign salivary tumour
  • Affects almost exclusively the parotid gland
  • Typified by bilayered oncocytic epithelium, cyst formation and lymphoid stroma
  • RF - SMOKING, prior RTX, viral (EBV/HPV/HIV) and exposures - nickel, rubber, hairdresser
  • Minimal risk of malignant transformation
  • Can avoid surgery and monitor if no sx
  • Presents with painless lump
  • Work up with USS/CT/MRI and FNA/core
  • Mx is superficial parotidectomy and facial nerve preservation
  • Minimal benefit for doing total even if deep component is involved

Malignant

Histology

  • Features of malignancy
    • Invasion
    • PNI/LVI
    • Necrosis

Theories of Development

Multicellular hypothesis - Arise from mature epithelium in various parts of salivary unit

  • Reserve cell hypothesis
    • Arise from undifferentiated or pluripotent cells

Types

  • Mucoepidermoid carcinoma
  • Adenoid cystic carcinoma
  • Carcinoma ex pleomorphic adenoma

Grades

  • Help to determine type of resection
    • Low grade = only low grade mucoepidermoid carcinoma
      • Superficial parotidectomy
    • High grade = high grade mucoepidermoid carcinoma, adenoid cystic carcinoma and carcinoma ex pleomorphic adenoma
      • Total parotidectomy UNLESS
    • Located peripherally → superficial parotidectomy

Mucoepidermoid carcinoma

Definition

  • Malignant neoplasm of the parotid gland and other salivary glands

Epidemiology

  • F=M, age 40-50
  • Most common salivary gland malignancy
  • 1% of all cancers
  • 5% of all H+N cancers

Risk Factors

  • Radiation (ionizing radiation and H+N irradiation)
  • Viral - EBV, HIV
  • Immunosuppression
  • Exposure - rubber and nickel

Pathology

  • Macro
    • Poorly circumscribed mass with incomplete capsule
    • Cystic components
  • Micro
    • Mucous, intermediate and epidermoid cells
    • Mixed features

Clinical

  • Painless swelling
  • Facial nerve palsy - invasion
  • Fixed, solid

Investigations

  • USS - well circ, hypoechoic, cystic component
  • CT - same + higher grade = solid with infiltration
  • MRI - solid high grade hypo T2, poor defined margins, PNI
  • FNA/Core - core for grading is better

Staging

  • Distant mets to lung, bone and liver so need CT CAP

Management

  • Resectable, no distant mets and fit
    • Surgical resection with R0 resection
      • Superficial vs total and facial nerve
    • Neck dissection
      • Clinically positive - neck dissection
      • Clinically negative - elective neck dissection if high risk
        • Locally advanced, high grade, facial nerve involvement, LVI
    • Adjuvant radiation - high risk
  • Unresectable, distant mets, unfit
    • Primary radiation
    • Palliative chemo (poor response)

Prognosis

  • High risk features - + margins, cervical mets, aggressive histo/grade, PNI/LVI, extraglandular extension
  • Determined by - stage, site, margins
  • 60% 5YS adults

Adenoid Cystic Carcinoma

  • Definition
    • Same - Malignant neoplasm of the parotid gland and other salivary glands
  • Epidemiology
    • Same, age 50-60
  • Risk Factors
    • Same
  • Pathology
    • Macro - infiltrative firm mass
    • Micro - biphasic with ductal and myoepithelial differentiation, tubular/cribriform/solid
  • Clinical, investigations and management
    • Same
  • Prognosis
    • 5YS 80%
    • 15YS 30%

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