Blair Incision, Modified Blair Incision, and Extended Blair Incision

1. Blair Incision (Original)

• A straight preauricular incision running vertically in front of the ear, curving slightly inferior to the ear lobule
• It provides direct access to the parotid gland but has limited exposure of the neck and is rarely used in its original form today

2. Modified Blair Incision (Bailey's Modification / "Lazy-S")

Flap elevation technique (Bailey & Love)

1. The horizontal (cervical) component is incised first to identify the platysma, the external jugular vein, and the greater auricular nerve
2. The vertical (preauricular) component is then incised and connected inferiorly
3. A subplatysmal flap is raised - the platysma is divided, and the flap is elevated remaining below the SMAS (superficial musculoaponeurotic system), lifting subcutaneous fat off the parotid gland
4. Flap elevation proceeds anteriorly over the parotid but not onto the masseteric fascia, to avoid damaging nerve branches exiting the gland

Indications

• Superficial parotidectomy
• Total parotidectomy
• Combined parotidectomy + neck dissection (the cervical limb permits excellent neck access)
• First branchial cleft anomalies (Work type II) - allows identification of the facial nerve trunk
• Both benign and malignant parotid tumours

3. Extended Blair Incision

• An extended Blair incision is made to raise a cervicofacial flap
• It allows identification and preservation (or controlled sacrifice) of the facial nerve trunk and major branches
• Used when resection involves structures such as the nasopharynx/oropharynx, infratemporal fossa, petrous ICA, or cavernous sinus

Comparison Summary

Alternatives: The Facelift Incision

• The preauricular portion is similar to the modified Blair
• The posterior limb curves at right angles behind the ear, into the hairline, avoiding any visible neck incision
• It offers superior cosmesis but limited neck access - making it unsuitable when simultaneous neck dissection is needed
• A 2021 meta-analysis (PMC8677756) compared the two approaches

Doubly Modified Blair Incision

What it is

The Two Modifications

Purpose and Indications

"The operation is performed through a doubly modified Blair's incision as in a routine parotidectomy with a slight anterior extension of the cervical incision."

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery (Vol. 1), Chapter 11 - Parapharyngeal space tumours

• Deep lobe parotid tumours extending into the parapharyngeal space (e.g., "dumbbell tumours" - pleomorphic adenoma with a deep lobe component passing through the stylomandibular tunnel)
• Vascular parapharyngeal tumours - the cervical limb gives access to the carotid artery and internal jugular vein for proximal control
• Malignant lesions of the parapharyngeal space requiring parotidectomy + neck dissection
• Cases where a standard parotidectomy is combined with wide posterior and inferior flap mobilisation

Why the Retroauricular Limb Matters

1. Posterior flap mobilisation - allows the skin/SMAS flap to be reflected further anteriorly without tension, improving access to the deep lobe and parapharyngeal space
2. Mastoid and stylomastoid foramen access - facilitates retrograde facial nerve identification in difficult or revision cases
3. Vascular pedicle protection - prevents flap ischaemia at the angle between the preauricular and cervical limbs by reducing tension at the curve behind the lobule
4. Extensibility - can be extended superiorly into the temporal hairline if skull base access is required (merging with the extended Blair concept)

Progression of Blair Incision Variants

Original Blair (1918)
  ↓ + cervical limb toward mastoid/SCM
Modified Blair (Bailey, 1941) = "lazy S"
  ↓ + retroauricular limb behind the ear
Doubly Modified Blair
  ↓ + temporal scalp extension
Extended Blair (for skull base / infratemporal fossa)

Benign Tumours of the Parotid Gland

Overview and Epidemiology

WHO Classification of Benign Epithelial Salivary Gland Tumours

1. Pleomorphic Adenoma (Benign Mixed Tumour)

Epidemiology

• Most common salivary gland tumour overall - 50% of all salivary gland tumours, 65% of parotid tumours, 40% of minor salivary gland tumours
• Annual incidence: 2.4-3.05 per 100,000
• Peak age: 3rd-6th decade; average presentation age 45 years
• More frequent in women
• Predominantly in the superficial lobe of the parotid; a significant proportion arise in or involve the deep lobe
• Can also arise from accessory parotid tissue along the parotid duct, the submandibular gland, or minor salivary glands (e.g. soft palate)

Clinical Features

• Painless, well-defined, solitary, mobile mass with gradual progression over many years
• Can reach enormous proportions if untreated

• Deep lobe tumours may present as a paratonsillar bulge
• Sudden increase in size or facial nerve palsy suggests malignant transformation

Pathology

1. Ductal (epithelial) cells - form ducts, acini, tubules, or sheets
2. Myoepithelial cells - spindle, plasmacytoid, clear cell, or epithelioid morphology
3. Chondromyxoid stroma - the most characteristic feature; may contain true cartilage, calcification, or even bone (the only salivary tumour to do so)

The Capsule - Critical Surgical Point

• The capsule is exceptionally thin (<20 microns) in at least one area in virtually all pleomorphic adenomas
• Incomplete in ~50%, especially the myxoid/mucoid type (most prone to operative rupture)
• Rupture during surgery seeds the operative field and significantly increases the risk of multifocal recurrence
• This is why enucleation is absolutely contraindicated - recurrence rate after simple enucleation approaches 25%, vs ~4% after formal parotidectomy

Risk of Malignant Transformation (Carcinoma Ex Pleomorphic Adenoma)

• Overall risk: ~6% (Scott-Brown's); correlates strongly with duration:
  • <5 years: ~2%

  • 15 years: ~10% (Robbins)

• Risk factors: older age, male sex, long duration, multiple recurrences, deep lobe location
• The resultant carcinoma is among the most aggressive of salivary gland malignancies: mortality 30-50% at 5 years

Treatment

• Partial superficial parotidectomy (tumour + cuff of normal tissue) - most common practice in UK
• Total superficial parotidectomy for larger tumours or where cuff cannot be achieved
• Deep lobe tumours: total parotidectomy, usually via a transcervical-transparotid approach
• Submandibular gland: excision of the entire gland (extracapsular)
• Minor salivary glands: wide local excision
• Enucleation must be avoided

2. Warthin's Tumour (Adenolymphoma / Papillary Cystadenoma Lymphomatosum)

Epidemiology

• Second most common benign parotid tumour (5-15% of benign parotid tumours; up to 20% by some series)
• Almost exclusively in the parotid gland - rare in the submandibular gland (which contains no lymphoid tissue)
• Peak incidence: 6th-7th decade
• Formerly quoted as strongly male-predominant (10:1); more recent series show male:female ratio of only ~1.6:1, suggesting sex distribution is becoming more equal
• Strong association with cigarette smoking (risk increased 8-fold) and secondly with radiation exposure
• Rare in Afro-Caribbeans/Black Africans; more common in Caucasians and Asians
• Multifocal in ~10%, bilateral in 4-10% of cases - the most commonly bilateral salivary gland tumour
• Can occur synchronously with pleomorphic adenoma

Clinical Features

• Slow-growing, soft, painless swelling at the lower pole of the parotid gland
• Facial palsy is rare

Pathology

1. Bilayered oncocytic epithelium - inner columnar + outer cuboidal cells; the term "oncocyte" refers to large cells with abundant granular eosinophilic cytoplasm packed with mitochondria; papillary projections lining cysts
2. Reactive lymphoid stroma with germinal centres (explains the near-exclusive parotid location - the parotid uniquely contains intraparotid lymph nodes where ductal epithelial inclusions are thought to give rise to the tumour)

Malignant Transformation

• Extremely rare (<1%) and may represent dual pathology rather than true transformation
• Can be carcinomatous (adenocarcinoma, SCC, or undifferentiated) or lymphomatous change

Treatment

• FNAC is often diagnostic
• Formal excision: partial superficial parotidectomy
• Given the very low malignant potential, the elderly age group, and the possibility of no growth, conservative observation alone is acceptable in selected patients
• Recurrence after excision: very rare (~2%), may represent multifocal disease

3. Other Benign Parotid Tumours (Less Common)

Oncocytoma

• Composed entirely of oncocytes (mitochondria-rich cells)
• Rare, <1% of salivary gland tumours
• Older patients; treated by surgical excision

Myoepithelioma

• Composed almost entirely of myoepithelial cells (no ductal differentiation, unlike pleomorphic adenoma)
• Most common in the parotid
• Treated by excision

Basal Cell Adenoma

• Uniform basaloid cells; no chondromyxoid stroma (distinguishes from pleomorphic adenoma)
• Most common in the parotid
• Low recurrence rate; treated by excision

Canalicular Adenoma

• Almost exclusively in minor salivary glands (especially upper lip)
• Rare in parotid

Benign Mesenchymal Tumours (within or adjacent to the parotid)

• Schwannoma/Neurilemmoma - benign encapsulated tumour from Schwann cells; may arise from the facial nerve or its branches within the parotid; NF2 gene inactivation in 67%
• Haemangioma - most common benign parotid tumour in children; may involute spontaneously
• Lipoma, fibroma, lymphangioma (rare)

Summary Comparison

Pleomorphic Adenoma of the Parotid Gland

Definition and Nomenclature

Epidemiology

• Annual incidence: 2.4-3.05 per 100,000
• Accounts for ~50% of all salivary gland tumours, 65% of parotid tumours, and 40% of intraoral minor salivary gland tumours
• Can occur at any age, but most commonly between the 3rd and 6th decade (average age of presentation: 45 years)
• More frequent in women
• Radiation exposure is the one established risk factor

Sites

• Parotid gland >80% - most commonly within the superficial lobe, but a significant proportion arise from or involve the deep lobe by direct growth
• Can also arise from accessory parotid tissue along the duct (only visible when mouth opens as coronoid pushes it anteriorly)
• Submandibular gland
• Hard palate and other minor salivary glands (most common minor salivary site: hard palate)

Clinical Features

• Painless, well-defined, solitary, mobile mass with slow, gradual progression over many years
• Can reach enormous size if untreated

• Deep lobe tumours: present as a paratonsillar bulge or oropharyngeal mass
• Sudden increase in size or facial nerve palsy = red flags for malignant transformation
• Occasional metachronous or synchronous tumours
• Deep lobe tumours may present with dysphagia or a "dumbbell" parapharyngeal mass

Pathology

Macroscopic Appearance

• Well-demarcated, rounded/ovoid with broad-based bosselations
• Variably encapsulated - capsule may be thick and fibrotic or attenuated and incomplete
• Cut surface: solid, homogeneous or variegated blue/grey hue from chondromyxoid matrix; may show cystic change, calcification, or cartilage

Microscopic Appearance

1. Ductal (epithelial) elements - cuboidal to columnar cells forming ducts, acini, tubules, strands, or sheets
2. Myoepithelial cells - arranged as spindle, plasmacytoid, epithelioid, or clear cells; form the outer layer of duct structures
3. Chondromyxoid (mesenchymal) stroma - the most characteristic feature; loose myxoid tissue with islands of cartilage (though often called "pseudo-cartilage" it is true cartilage histologically), hyaline tissue, and rarely bone - calcification or bone formation is found only in pleomorphic adenoma among salivary gland tumours, making it pathognomonic

Immunohistochemistry

Molecular Genetics

• Many cases: chromosomal rearrangements causing overexpression of PLAG1 (transcription factor promoting growth factor receptor signalling genes)
• Cases lacking PLAG1 overexpression: HMGA2 gene mutations (encodes a DNA-binding protein)
• All tumour elements - including the apparently mesenchymal stroma - are thought to be of intercalated duct reserve cell (stem cell) and myoepithelial cell origin

The Capsule - The Central Surgical Problem

• The capsule is exceptionally thin (<20 microns) in at least one area in virtually all pleomorphic adenomas
• Incomplete in approximately 50%, especially the myxoid/predominantly mucoid type
• Myxoid stroma can bulge into normal gland parenchyma without any capsule intervening
• The predominantly mucoid types are semi-fluid and fluctuant - highly prone to intraoperative capsular rupture and spillage, seeding the operative field
• Such recurrences are typically multifocal

• Recurrence rate after simple enucleation: ~25%
• After formal parotidectomy with cuff: ~4%
• Even with "standard" superficial parotidectomy: 81% had some degree of capsule exposure, and >50% of surface was exposed in 60% of cases - meaning a capsule-free margin is practically impossible to achieve consistently adjacent to the facial nerve

Investigations

FNAC (Fine Needle Aspiration Cytology)

• Standard first-line investigation
• Diagnostic or strongly suggestive in most cases
• Milan reporting system now used for salivary gland FNAC

Ultrasound

• First-line imaging; characterises the mass, guides FNAC
• Pleomorphic adenoma: well-defined, hypoechoic, lobulated mass

MRI (Gold Standard for Imaging)

• T1: intermediate signal; T2: high signal (due to chondromyxoid matrix)
• Lobulated heterogeneous mass, typically posterior to the retromandibular vein
• Recurrent pleomorphic adenoma: single or multiple T2 hyperintense masses within the parotidectomy bed
• Mandatory in recurrent disease to detect multifocal foci and assess residual parotid tissue

CT

• Useful to detect calcification; assesses bony involvement in deep lobe/skull base tumours

Surgical Management

Indications for Surgery

1. Definitive histology - imaging and FNAC cannot completely exclude malignancy
2. Continued growth if left untreated
3. Risk of malignant transformation

The Controversy: Extent of Parotidectomy

Deep Lobe Tumours

• Generally require total conservative parotidectomy (facial nerve preserved)
• Smaller deep lobe tumours: limited superficial partial parotidectomy to gain access via inferior branches, then ECD of deep lobe tumour
• Parapharyngeal space extension: transcervical-transparotid approach (doubly modified Blair incision); transmandibulotomy if large and anterior; TORS as an emerging alternative

By Location

Recurrence

• Overall recurrence rate: ~2-6.7% (depending on series; Dutch national database showed 6.7% over 20 years)
• Typically presents ~1 decade after original surgery
• Most recurrences are multicentric (multifocal seedling pattern)

Management of Recurrence

• MRI is mandatory - characterises recurrence(s), detects further foci, assesses residual parotid
• Repeat FNAC - do NOT rely on original histology
• Original histology reviewed by a head and neck pathologist
• The key principle: treat the first recurrence as the last good opportunity for cure with facial nerve preservation - all remaining parotid tissue should be resected with all recurrence foci
• Surgical skills needed: retrograde nerve branch dissection; facial nerve identification in mastoid; nerve repair/cabling by micro-anastomosis
• Post-operative radiotherapy considered after comprehensive resection - effective in reducing further recurrence
• Malignant change in recurrent tumours: ~3% (higher than in primary disease)
• Second recurrence after radiotherapy is challenging and may require temporal bone resection, mandibulectomy, and reconstruction

Malignant Transformation: Carcinoma Ex Pleomorphic Adenoma

• Overall risk: ~6% (Scott-Brown's); strongly time-dependent (Robbins):
  • Present <5 years: 2%
  • Present >15 years: 10%
• Risk factors: older age, male sex, long duration, multiple recurrences, deep lobe location
• Presents as a rapidly growing mass (within a longstanding swelling) + pain + facial palsy
• More common in women; presents a decade later than primary PA (6th decade)
• Histology: Variable proportions of pleomorphic adenoma + high-grade adenocarcinoma (salivary duct carcinoma or myoepithelial carcinoma)
• Subclassification:
  • Non-invasive / intracapsular (confined within PA)
  • Minimally invasive (breaching capsule)
  • Widely invasive (into adjacent salivary gland and soft tissue)
• Molecular: TP53 mutations; HER2 amplification (in salivary duct carcinoma component)
• Prognosis: Among the most aggressive salivary malignancies - local and distant metastases in 70%; 5-year survival only 25-65%
• Treatment: Radical surgical excision ± adjuvant radiotherapy

Key Summary Points