---

Important Questions in Salivary Gland Tumours

1. Epidemiology and General Rules

• Salivary gland neoplasms are rare, forming <3% of head and neck malignancies
• Incidence: 0.4-13.5/100,000 for benign; 0.4-2.6/100,000 for malignant tumours
• Present after the 4th decade; affect both sexes equally
• >80% occur in major salivary glands and the majority are benign
• "Rule of 80s" (Parotid gland): 80% of salivary tumours are in parotid; 80% of parotid tumours are benign; 80% of benign parotid tumours are pleomorphic adenomas

---

2. WHO Classification (2017) - Key Types

• Pleomorphic adenoma (commonest overall)
• Warthin's tumour (adenolymphoma)
• Oncocytoma
• Basal cell adenoma
• Canalicular adenoma

• Mucoepidermoid carcinoma (commonest malignant)
• Adenoid cystic carcinoma
• Acinic cell carcinoma
• Carcinoma ex pleomorphic adenoma
• Salivary duct carcinoma
• Polymorphous low-grade adenocarcinoma

• High grade: High-grade mucoepidermoid carcinoma, salivary duct carcinoma, adenoid cystic carcinoma, carcinoma ex pleomorphic adenoma, squamous cell carcinoma, anaplastic/undifferentiated carcinoma, malignant mixed carcinoma
• Low grade: Low-grade mucoepidermoid carcinoma, acinic cell carcinoma, polymorphous low-grade adenocarcinoma

---

3. Pleomorphic Adenoma (Mixed Parotid Tumour)

• Commonest benign salivary gland tumour overall
• Commonest salivary gland tumour in children
• Most common in parotid gland (80%); also submandibular, hard palate
• Slightly more common in women
• Presents as painless, well-defined, solitary mobile mass with slow progression over years
• Deep lobe tumour may present as paratonsillar bulge (dumbbell tumour)

• Sudden rapid increase in size
• Onset of facial nerve palsy
• Pain

• Mixed epithelial, myoepithelial, and stromal components
• Stroma is myxoid/chondroid/hyalinised
• IHC: luminal cells express CK7; myoepithelial cells express p63, S-100, SOX10, SMA
• Variable encapsulation - areas of deficient capsule are common (predisposes to recurrence)

• Superficial/total parotidectomy with facial nerve preservation
• Enucleation is CONTRAINDICATED - risks capsular breach and spillage, leads to recurrence
• Facial nerve monitoring should be used during parotid surgery

---

4. Warthin's Tumour (Adenolymphoma / Cystadenoma Lymphomatosum)

• 2nd most common benign salivary gland tumour (5-15%)
• Almost exclusively in parotid gland (inferior pole)
• Predominantly in older men (after 6th decade)
• Strong association with cigarette smoking and radiation exposure
• Can be bilateral (synchronous or metachronous); also occur with other salivary neoplasms

• Oncocytic bilayered epithelium lining ductal/papillary/cystic spaces
• Set in reactive lymphoid stroma with germinal centres
• Epithelium may show metaplastic changes (squamous, sebaceous, mucous cells)

---

5. Mucoepidermoid Carcinoma

• Commonest salivary gland malignancy overall
• Commonest malignant salivary tumour in children and young adults (peak: 2nd decade)
• Known to occur following childhood radiation or chemotherapy
• Most common site: parotid gland

• Demonstration of focal intracellular mucin is essential for diagnosis of high-grade type
• Treatment: Complete surgical excision; adjuvant radiotherapy for intermediate-high grade

---

6. Adenoid Cystic Carcinoma (AdCC)

• Slow-growing but highly malignant with a deceptively indolent course
• Composed of epithelial and myoepithelial cells
• Most common malignancy of minor salivary glands (palate is #1 minor salivary site)
• Notorious for perineural invasion - causes pain, facial nerve palsy along nerve distribution
• Tends to metastasise to cervical nodes and lung

1. Cribriform (Swiss cheese pattern) - most common
2. Tubular - bilayered tubules with true lumen
3. Solid - sheets and nests; least common; worst prognosis

• Ductal cells: c-KIT positive
• Myoepithelial cells: p63 and SMA positive

---

7. Acinic Cell Carcinoma

• Low- to intermediate-grade tumour
• 90% occur in parotid gland
• Slight female predilection (1.5:1); peak in 5th decade
• Slow-growing, painless, mobile; rarely presents with facial palsy
• IHC: positive for DOG1 and SOX10; negative for mammaglobin (distinguishes from secretory carcinoma)

---

8. Carcinoma ex Pleomorphic Adenoma

• Arises from primary or recurrent pleomorphic adenoma
• More common in women; presents a decade later than pleomorphic adenoma (6th decade)
• Typically in parotid gland
• Classic presentation: rapidly growing mass within a longstanding swelling, with pain and facial palsy
• Local and distant metastases in 70% of cases; poor 5-year survival: 25-65%
• Molecular: TP53 mutations and HER2 amplification (especially in salivary duct carcinoma component)

1. Non-invasive/intracapsular
2. Minimally invasive (tumour breaching capsule)
3. Widely invasive

---

9. Salivary Duct Carcinoma

• Also called high-grade ductal carcinoma
• Resembles high-grade invasive ductal breast cancer histologically (comedo necrosis, cribriform/Roman bridge pattern)
• Occurs mainly in parotid gland; more common in older men
• Presents with facial palsy, pain, rapid growth, and cervical lymphadenopathy
• Androgen receptor (AR) and HER2 positive - targetable in recurrent/metastatic setting
• Treatment: Total parotidectomy + neck dissection + adjuvant radiotherapy
• High predilection for local recurrence and distant metastases; poor overall survival

---

10. Investigations

• Ultrasound - first-line investigation; benign tumours appear as well-lobulated hypoechoic lesions; malignant = irregular, inhomogeneous with blurred margins
• CT scan - better for osseous involvement, extraglandular extension, nodal disease
• MRI (including DW-MRI and gadolinium-enhanced dynamic MRI) - best differentiates benign from malignant; uses ADC values and washout ratios; preferred for deep lobe and skull base involvement
• PET-CT - used for distant metastases in high-grade tumours

• Fine-needle aspiration cytology (FNAC) - first-line tissue diagnosis; performed under ultrasound guidance
• Tru-cut biopsy is an alternative (second-line)
• Open biopsy is contraindicated (risk of tumour seeding)

---

11. AJCC Staging (T staging for major salivary glands)

---

12. Treatment Principles for Malignant Tumours

• Surgery is the mainstay - aim for microscopic margins of at least 0.5 cm
• Extent is determined by size, stage, and grade
• Facial nerve preservation is planned but not at the cost of residual disease
• Elective neck dissection for T3/T4 and high-grade tumours
• Comprehensive neck dissection is mandatory in node-positive disease
• Adjuvant radiotherapy for: Stage III/IV, high grade, close/positive margins, perineural or lymphovascular invasion, nodal metastasis with extranodal extension

---

13. Key Associations to Remember (Exam High-Yield)

---

---

Important Exam Questions - Salivary Gland Tumours

---

• 80% of all salivary tumours are in the parotid
• 80% of parotid tumours are benign
• 80% of those benign tumours are pleomorphic adenomas

• Parotid ~20%, Submandibular ~50%, Minor salivary glands >50%, Sublingual ~80%

• Cribriform (Swiss cheese) - most common
• Tubular
• Solid - worst prognosis

• Sudden rapid increase in size
• Onset of facial nerve palsy
• Pain

• Ductal cells: c-KIT positive
• Myoepithelial cells: p63, SMA positive

• T4a: invades skin, mandible, ear canal, or facial nerve
• T4b: invades skull base, pterygoid plates, or encases carotid artery

---