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Oral (Salivary) Gland Diseases and Tumors: A Surgical Framework

1. The Glands - Anatomy That Drives Surgical Risk

There are four groups of salivary glands, each carrying unique surgical implications:

Gland	% of all SGTs	% Malignant	Key Surgical Risk
Parotid	~70%	~20%	Facial nerve (CN VII)
Submandibular	~15%	~50%	Marginal mandibular branch, lingual n., hypoglossal n.
Sublingual	~5%	~75%	Lingual nerve
Minor salivary	~10%	~80%	Site-dependent

The rule of thumb: As gland size decreases, the proportion of malignant tumors increases (roughly 25% / 50% / 75% for parotid / submandibular / sublingual or minor glands).

The parotid gland develops with late encapsulation, which embeds vessels, nerves, and lymph nodes within it. The facial nerve traverses it - dividing it into a superficial lobe (lateral to nerve) and deep lobe (medial to nerve). Patey's faciovenous plane separates these two lobes and is the central anatomical concept in parotid surgery.

2. Classification of Salivary Gland Tumors

Benign Tumors

Tumor	Key Features
Pleomorphic adenoma (benign mixed tumor)	Most common (53-77% of all parotid tumors). Biphasic: epithelial + myoepithelial/mesenchymal (cartilaginous) components. Has "pseudopodia" - needs margin, not enucleation. ~6% risk of malignant transformation (carcinoma ex-PA) that rises with time
Warthin tumor (papillary cystadenoma lymphomatosum)	Second most common. Male smokers. Bilateral in ~10%. Located in parotid tail. Can be observed in some cases
Basal cell adenoma	Rare. Well-circumscribed
Oncocytoma	Rare. Older patients
Hemangioma	Most common parotid tumor in infants

Malignant (Primary) Tumors

Tumor	Grade	Key Features
Mucoepidermoid carcinoma (MEC)	Low/intermediate/high	Most common parotid malignancy. History of radiation. Can occur in children. Mucous + epidermoid cells
Adenoid cystic carcinoma (AdCC)	Intermediate	Most common malignancy of submandibular and minor glands. Perineural invasion is hallmark. Skip lesions along nerves. Cribriform/tubular/solid patterns. Long indolent course but late distant mets
Adenocarcinoma	High	Aggressive
Acinic cell carcinoma (ACC)	Low	>90% in parotid. Second most common in children. Wide age range
Carcinoma ex-pleomorphic adenoma	High	Malignant transformation of a pre-existing PA. Poor prognosis
Salivary duct carcinoma	High	HER2-positive. Aggressive. Resembles ductal carcinoma of breast
Polymorphous adenocarcinoma (PAC)	Very low	Almost exclusively minor salivary glands (hard palate). Perineural invasion but excellent prognosis

Malignant Non-Salivary / Metastatic

Lymphoma, squamous cell carcinoma (skin metastasis to parotid nodes), melanoma.

3. Clinical Red Flags for Malignancy

A parotid mass is considered potentially malignant if there is:

Pain (unusual in benign tumors)
Rapid growth
Facial nerve palsy (partial or complete)
Skin fixation or ulceration
Cervical lymphadenopathy
Trismus (masseter/pterygoid invasion)
Prior skin cancers of the face (potential parotid lymph node metastasis)

4. Investigation Strategy

Ultrasound - first-line imaging. Distinguishes intrinsic vs. extrinsic mass. Guides FNAC.
Fine Needle Aspiration Cytology (FNAC) - essential. Distinguishes benign from malignant in ~79% of cases. Incisional biopsy is contraindicated in the parotid (risk of fistula and facial nerve injury). FNAC alone is not sufficient for full histologic typing.
CT with contrast or MRI - for deep lobe tumors, parapharyngeal extension, bone invasion, perineural spread, and nodal staging.

CT clue: A dumbbell-shaped tumor with a narrow isthmus through the stylomandibular tunnel = deep lobe extension of pleomorphic adenoma.

CT showing large pleomorphic adenoma with dumbbell appearance - superficial and deep lobe components

CT axial: Large pleomorphic adenoma involving both lobes of the parotid, with the dumbbell isthmus (black arrowheads) passing through the stylomandibular tunnel. Fat of parapharyngeal space displaced medially (white arrowhead), carotid displaced posteriorly. - Cummings Otolaryngology

5. TNM Staging for Major Salivary Gland Cancers

Stage	Definition
T1	≤2 cm, no extraparenchymal extension
T2	>2 cm but ≤4 cm, no extraparenchymal extension
T3	Extraparenchymal extension WITHOUT CN VII involvement, OR >4 cm but ≤6 cm
T4	Invades skull base, CN VII, OR >6 cm

6. Surgical Decision Framework

Before operating, four decisions must be made (from Bailey and Love's):

Presumed tumor histology (benign vs. malignant)
Relation to facial nerve plane (superficial vs. deep to Patey's faciovenous plane)
Location (superficial lobe, deep lobe, parapharyngeal extension)
Facial nerve function (pre-operative palsy = major concern)

Types of Parotid Surgery (conservative to radical)

Procedure	Indication	Nerve
Extracapsular dissection (ECD)	Select small benign tumors, avoids formal nerve dissection	Preserved (visualized, not formally traced)
Adequate parotidectomy	Tail lesions - tumor + cuff of normal tissue	Preserved
Superficial parotidectomy	Tumors lateral to facial nerve plane (most PAs)	Preserved by formal dissection
Total conservative parotidectomy	Tumors crossing or involving deep lobe	Preserved (nerve skeletonized)
Radical parotidectomy	Malignancy with extraparenchymal spread and nerve invasion	Sacrificed - immediate reconstruction with graft

7. Superficial Parotidectomy - Step-by-Step

Right superficial parotidectomy - Modified Blair incision, flap elevation, facial nerve identification, and pes anserinus

Fig: Right superficial parotidectomy. (A) Modified Blair incision. (B) Flap elevation - parotid fascia (PF), platysma (PM), parotid tail (PT), SCM. (C) Main trunk of facial nerve identified: tragal pointer (arrowhead), posterior digastric (DGM), nerve (arrow), bifurcation (asterisk). (D) Pes anserinus after complete superficial lobe removal. - Cummings Otolaryngology

Key Steps:

1. Position and Incision

Supine, head rotated away
Modified Blair incision: preauricular crease → around ear lobule → over mastoid tip → curves down along SCM → skin crease in upper neck
Alternative: Facelift incision for better cosmesis in benign lower/middle parotid tumors (entirely post-auricular)
Lazy-S incision (Bailey & Love): three components - horizontal (2 finger-breadths from mandible angle), vertical (close to tragus), and communicating curve

2. Flap Elevation

Subplatysmal flap in cervical portion
Superficial to parotid fascia in preauricular region
Do NOT go onto masseteric fascia - facial nerve branches exit here
Identify and divide greater auricular nerve and external jugular vein to free the parotid tail

3. Parotid Mobilization

Dissect off SCM
Expose posterior belly of digastric → trace to mastoid
Free gland from tragal cartilage and bony EAC → expose the tragal pointer
Identify tympanomastoid suture

4. Facial Nerve Identification - the Critical Step

The nerve lies ~1 to 1.5 cm deep and inferior to the tragal pointer. Landmarks in order of reliability:

Tragal pointer (most commonly used): nerve is just deep and inferior to it
Tympanomastoid suture: follow medially to the stylomastoid foramen
Posterior belly of digastric: nerve exits stylomastoid foramen just superior to its attachment

5. Centripetal Dissection

Once main trunk found, dissect in Patey's plane using fine curved artery forceps
Glandular tissue divided laterally, working branch by branch
Start with lower cervicomandibular division (cervical → marginal mandibular → lower buccal)
Then trace upper temporozygomatic division (temporal → zygomatic → upper buccal)
All branches followed until specimen remains attached only to parotid duct
Clamp and ligate the duct to deliver specimen

6. Total Conservative Parotidectomy

After superficial lobe removal, dissect deep lobe off temporal veins and terminal external carotid branches
Nerve is fully skeletonized but preserved

7. Radical Parotidectomy

Malignancy with extraparenchymal spread and nerve invasion
Remove all gland + involved facial nerve branches + surrounding structures (commonly masseter)
Immediate reconstruction: cable grafts from greater auricular nerve or sural nerve
Priority: orbicularis oculi (eye closure) and orbicularis oris branches

8. Treatment by Tumor Type

Benign Tumors

Pleomorphic adenoma: Superficial parotidectomy with facial nerve preservation. Tumor has pseudopodia - resect with a margin of normal gland. Do not enucleate - tumor spillage causes multifocal recurrence in the operative bed. Radiotherapy can provide local control for multiply recurrent cases.
Warthin tumor: Can be observed; if operated, superficial parotidectomy or ECD.

Low-Grade Malignancy (ACC, polymorphous adenocarcinoma)

Parotidectomy alone is adequate
Neck dissection only if clinical/proven adenopathy
Adjuvant radiation for stage III/IV, perineural invasion

High-Grade Malignancy (salivary duct carcinoma, high-grade MEC, carcinoma ex-PA, most adenocarcinomas)

Total or radical parotidectomy
Ipsilateral neck dissection mandatory (supraomohyoid or comprehensive depending on nodal status)
Adjuvant radiation

Adenoid Cystic Carcinoma

Wide surgical margins required
Perineural invasion demands extensive resection along nerve planes
Radiation fields must include nerve pathways up to skull base
Preserve facial nerve if functional and not grossly invaded - even if malignant

Facial Nerve Management in Malignancy

If nerve not paralyzed preoperatively AND not directly invaded by pathology-confirmed tumor: preserve the nerve
If nerve sacrificed: immediate nerve graft reconstruction (greater auricular or sural nerve)
Gold weight implant in upper eyelid to improve eye closure when orbicularis oculi branch is sacrificed

9. Submandibular Gland Excision

Three critical nerves at risk:

Marginal mandibular branch of CN VII (motor - depressor of lower lip)
Lingual nerve (sensory - tongue)
Hypoglossal nerve (CN XII) (motor - tongue)

Most common malignancy here: Adenoid cystic carcinoma

Surgery involves block dissection to remove entire contents of the submandibular triangle. For malignancy:

Marginal or segmental mandibulectomy if bone is involved
Supraomohyoid neck dissection if indicated

10. Complications of Parotidectomy

Complication	Mechanism	Notes
Facial nerve palsy	Temporary (traction/edema) or permanent (sacrifice)	Temporary palsy more common; resolves weeks-months
Frey syndrome	Auriculotemporal nerve regeneration to sweat glands (gustatory sweating)	Delayed onset post-op
First bite syndrome	Sympathetic denervation	Severe jaw pain on first bite of each meal
Sialocele / salivary fistula	Residual gland secretion	Usually resolves
Greater auricular nerve numbness	Division of nerve	Earlobe numbness
Scar/cosmetic deformity	Contour defect post-gland removal	Use of SMAS or fat grafts to fill defect

Summary of Key Teaching Points

Gland size inverse to malignancy risk - smaller gland = higher % malignancy
80% of parotid tumors are benign - most are pleomorphic adenoma
Never enucleate a pleomorphic adenoma - always include a cuff of normal tissue
Facial nerve preservation is the defining challenge in parotid surgery; nerve must always be identified at the main trunk before proceeding
Facial nerve palsy preoperatively = malignancy until proven otherwise
FNAC is the preferred biopsy - incisional biopsy is contraindicated in the parotid
Deep lobe tumors and parapharyngeal extension require CT/MRI pre-operatively
High-grade malignancy always requires neck dissection + adjuvant radiation
Adenoid cystic carcinoma has perineural spread as its hallmark - follow the nerve
Intraoperative nerve monitoring is recommended especially in revision surgery and suspected malignancy

Sources: Cummings Otolaryngology Head and Neck Surgery (9780323612173); Bailey and Love's Short Practice of Surgery 28th Edition (9780367548117); Mulholland and Greenfield's Surgery 7th Edition (9781975143169)

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