Salivary Gland
Introduction
- Three large, paired major glands
- Parotid
- Submandibular
- Sublingual
- Smaller, minor glands
- Throughout the lamina propria of the upper aerodigestive tract
- ~ 600-1000
- Most in oral cavity
- 50% in hard palate
- Salivary gland function is produce saliva
- 60% is produced by Parotid
- Each gland is composed of acini of mucinous or serous cells
- Myoepithelial cells surround the acinar cells
- Salivary ducts within each gland:
- Intercalated
- Striated
- Excretory
Anatomy
Parotid
- The anatomic isocenter is at the axial level at C2/C3
- Superficial to and partly behind the ramus of the mandible
- Covers the masseter muscle
- Posterior part of the muscle
- Fills the space between the ramus of the mandible and the anterior border of the sternocleidomastoid muscle
- Two lobes:
- Superficial
- Deep
- One or more isthmi connects these two lobes
- Facial nerve is wrapped through these isthmi
- Facial n. enters the deep surface of the gland as a single trunk —> passing posterolateral to the styloid process
- —> usually leaves the gland as five or more branches from ant, up and lower border of Parotid
- Facial n. is superficial to the main blood vessels that traverse the gland
- Lymphatics:
- Facial LN
- Downward along the retromandibular vein
- —> Superficial LN along the outer surface of the SCM —> deep cervical chain
- LN from parietal region of the scalp —> parotid nodes in front of the ear and partly to the retroauricular nodes in back of the ear, which, in turn, drain into upper deep cervical nodes
Submandibular Gland
- Has a superficial and deep portion
- Fills the triangle between the two bellies of the digastric and the lower border of the mandible
- On the lower surface of the mylohyoid and behind it
- Against the lateral surface of hypoglossus
- Inferior surface is adjacent to the submandibular LN
- Between the lingual nerve above and the hypoglossal nerve below
- Wharton's ducts
- Drain into the sublingual caruncles (caruncula sublingualis) on either side of the lingual frenulum along with the major sublingual duct (Bartholin).
- LN
- Submandibular
- Two LN posteriorly fo the facial a.
- —> anterior subdigastric nodes of the internal jugular chain(IJC)
Sublingual Gland
- Smallest
- Sup border —> floor of the mouth
- Inf border —> Mylohyoid m.
- Lat border —> Mandible
- Med border —> Genioglossus m.
- Rare for Ca
- LN
- Submandibular
- Submental (rare)
- IJC
Epidemiology
- Rare
- 0.4% of all ca
- < 5% of head and neck cmaliga
- White > other ethnicities
- However mucoepidermoid carcinoma & adenoid cystic carcinoma are equal
Location | Percentage of Salivary Gland Ca | Proportion of malignant tumours (vs all masses) |
---|---|---|
Parotid | 70% | 25% |
Submandibular | 10% | 40% |
Minor Salivary | 20% | 65% |
- Benign tumour —> F>M
- Malignant —> F=M
- Benign —> younger (45 yrs)
- Malignant —> (55 yrs)
- All salivary neoplasm in children are malignant
Epidemiologic difference between genders:
Gender | More common Paths |
---|---|
Male | Squamous Cell Ca, AdenoCa, Salivary Duct Ca |
Female | Acinic Cell Ca, Adenoid Cystic Ca |
- Most common nonsquamous salivary gland cancers:
- Males:
- Mucoepidermoid ca
- Adenocarcinoma
- Females:
- Mucoepidermoid
- Acinic cell
- Adenoid cystic ca
- Males:
Etiologic factors:
- Nutritional deficiencies
- Eskimos in Arctic —> Low Vit A & C
- Exposure to ionizing radiation
- Maybe more in Minor Salivary Gland
- UV light exposure
- Genetic predisposition
- History of previous cancer of the skin of the face
- Occupational exposure
- Hair dresser
- Beauty Salon
- Viral (EBV)
- Alcohol use
- Hair dye use
- Higher educational
- Smoking and Alcohol usually are NOT considered related
- Smoking >80 might be!!!
Women (if younger than 35) with salivary gland cancer may have a 2.5 elevated breast cancer risk
Natural History
Local invasion
- Parotid:
- 20% fixed
- 10% Skin invasion
- 25% Facial Palsy
- Invasion to External auditory canal
- drainage from ipsilateral ear
- Parapharyngeal space invasion
- Involvement of Pterygoid m. ==> Trismus
Lymph Node Involvement
- Histology
- SCC, Undiff Ca & Salivary duct Ca > Mucoepidermoid cancer > Acinic cell, Adenoid cystic carcinoma, ex-pleomorph adenoma
- Chance of contralateral LN(+) is very low (non-existent)
Tscore+Histology Score | Parotid | Submandibular | Oral Cavity | Other |
---|---|---|---|---|
2 | <5% | 0% | <5% | 0% |
3 | 10% | 30% | 10% | 30% |
4 | 25% | 60% | 20% | 50% |
5 | 30% | 60% | cell-content | cell-content |
6 | 35% | 60% | cell-content | cell-content |
T1 = 1, T2 = 2, T3-4 = 3;
acinic/adenoid cystic/carcinoma ex pleomorphic adenoma = 1, mucoepidermoid = 2, squamous/undifferentiated = 3
Distant Metastases
- Lung
- Bone
- Occasionally to the liver
- Overall:
- At presentation:3%
- After 10yr: 30%
- Common:
- Adenoid cystic
- Maybe a late event with no local recurrence
- @ 10yr —> 40%
- Survival 5yr after DM —> 40%
- Survival 10yr after DM —> 10%
- Salivary duct
- Squamous cell
- Undifferentiated carcinomas
- Adenoid cystic
Molecular Biology
- Mucoepidermoid Ca
- t(11;19)(q21;p13)
- Associated with better DFS and OS
- CDKN2A(p16) Mutation
- ==> increase invasiveness
- t(11;19)(q21;p13)
- Adenoid cystic Ca
- t(6:9)
- ==> MYB-NFIB fusion oncoprotein
- c-KIT/CD117 mutation
- t(6:9)
- Epidermal Growth Factor Receptor transmembrane receptor family
- EGFR
- ERBB2 (HER2/ neu)
- Reported for Salivary Gland
- Strong overexpression in mucoepidermoid & salivary duct ca
- Rare in adenoid Cystic
- Reported for Salivary Gland
Neoneurogenesis in Salivary Gland tumours
* Perineural invasion
* Adenoid cystic ca
- Mutual(دوطرفه) neurotropic interaction with cancer cells and neurons
- Release of various paracrine growth factors
- Brain-Derived Neurotrophic Factor (BDNF)
- Nerve Growth Factor (NGF)
- NGF receptor —> Tyrosine Kinase A (TrkA)
- Neurotropin staining —> positive in adenoid cystic carcinomas
Pathology
- The best prognosis is seen for acinic cell and (low-grade) mucoepidermoid cancer.
- The worst for un-differentiated and squamous cell cancer.
Clinical Presentation
- Painless, rapidly enlarging mass
- Benign —> for years
- Remember that 3/4 of Parotid mass are benign
- Malignant —> 3-6
- Benign —> for years
Malignant:
- Pain (10-20%)
- Facial Involvement (30%)
- Involvement of deeper structures (masseter, temporal, and pterygoid muscles)
- Base of skull invasion (rare)
- Pain and paralysis of various cranial nerves
Signs more common in malignant mass vs benign:
- Rapid growth rate
- Pain
- Facial nerve palsy
- Childhood occurrence
- Skin involvement
- Cervical adenopathy
Diagnostic Work-Up
- History
- Ask about pain
- change in facial grimace
- Peripheral Facial m. Palsy
- Physical Exam
- Full oral cavity exam
- Inspection
- Hard palate ( minor salivary )
- Posterior triangle —> Verify lesser and greater palatine foramina involvement
- Palatine nerves ( branch of Maxillary n. )
- Important specially in adenoid cystic
- Posterior triangle —> Verify lesser and greater palatine foramina involvement
- Hard palate ( minor salivary )
- Bimanual exam
- Inspection
- Cranial Nerve complete exam
- Regional adenopathy
- Full oral cavity exam
- Investigation:
- ALWAYS start with biopsy to confirm diagnosis
- FNA
- Blood work
- CBC
- KFT
- LFT
- CT
- MRI
- T1-weighted images are excellent to assess the margins, deep extent, and patterns of infiltration because the (fatty) background of the gland is hyperintensive
- T2-weighted
- Benign tumors are hyperintensive
- Malignant tumors are intermediate or low intensivity
- Sensitivity: 87%
- Specificity: 94%
- Verify Perineural invasion of adenoid cystic carcinoma
- ALWAYS start with biopsy to confirm diagnosis
Staging
page revision: 45, last edited: 29 Jul 2012 19:44