What is the diagnosis, treatment, and management of Warthin tumour, a rare benign salivary gland tumour, typically affecting older adults, particularly males and smokers, presenting with a painless lump in the parotid gland area?

Warthin Tumour: Comprehensive Overview

Definition and Epidemiology

Warthin tumour (papillary cystadenoma lymphomatosum) is a benign salivary gland neoplasm that accounts for 4-13% of all salivary gland tumours and represents the second most common salivary gland tumour after pleomorphic adenoma. 1

Key Demographic Features:

• Mean age at diagnosis: 62 years (range 12-92 years), with less than 6% presenting before age 40 1
• Strong male predominance (9:1 ratio in some series) 2
• Powerful association with tobacco smoking - affects predominantly heavy smokers 2
• Multicentric in 12-20% of patients 1
• Bilateral involvement in 5-14% of cases 1

Anatomical Distribution

Typical Location:

• Almost exclusively involves the parotid gland (>95% of cases), particularly the lower pole or tail 1, 3
• Periparotid lymph nodes may also be involved 4

Rare Extraparotid Sites:

• Submandibular gland: 0.4-6.9% of cases 1, 4
• Minor salivary glands: 0.1-1.2% (extremely rare) - reported in buccal mucosa 1
• Larynx: only 15 cases reported worldwide (supraglottic, glottic, or subglottic locations) 3
• Cervical lymph nodes: 8% 1

Clinical Presentation

Typical Features:

• Painless, slow-growing mass in the parotid region 1
• Asymptomatic nodular swelling in most cases 4
• No facial nerve involvement (distinguishes from malignancy) 5
• Soft, mobile, well-circumscribed mass on palpation 4

Important Clinical Distinction:

Unlike malignant salivary gland tumours, Warthin tumour does NOT present with facial paralysis, trismus, or cutaneous infiltration - these features suggest malignancy and require different management 6, 7

Diagnostic Workup

Standard Imaging:

• High-resolution ultrasound is the standard imaging modality (must be performed by trained personnel) 6
• MRI is highly valuable for accurate tumour detection and surgical planning, particularly for deep lobe tumours 5
• CT scan may be considered for cervico-facial assessment 6

Tissue Diagnosis:

• Fine-needle aspiration biopsy (FNAB) is an option for preoperative diagnosis 6
• Core needle biopsy (CNB) has higher sensitivity (94%) and specificity (98%) with lower inadequacy rates (1.2% vs 8% for FNAB) 6
• Risk stratification using the Milan System should be applied to cytology specimens 8
• Warthin tumour typically falls into Category IV (Benign Neoplasm) of the Milan System with very low malignancy risk 8

Pathological Features:

• Dual component architecture: epithelial (oncocytic cells arranged in papillary projections) and lymphoid stroma 4
• Cystic spaces lined by bilayered epithelium with underlying lymphoid tissue 4

Etiopathogenesis

Proposed Mechanisms:

• Heterotopic salivary gland tissue entrapped within lymph nodes 4
• Inflammatory reaction to tobacco smoke - some authors argue this represents an inflammatory process rather than true neoplasm 2
• Parotid duct involvement triggered by smoking 2
• Possible association with ionizing radiation 2

Treatment Strategy

Surgical Approach - The Definitive Treatment:

For Warthin tumour, enucleation or limited resection is the treatment of choice, NOT the extensive surgery required for malignant salivary gland tumours. 5

Specific Surgical Techniques by Location:

Superficial Lobe Tumours:

• Partial parotidectomy with tumour resection 5
• Enucleative procedure at the tumour base where capsule directly contacts facial nerve 5

Deep Lobe Tumours:

• Enucleation is recommended after accurate MRI detection 5
• More careful facial nerve preservation required due to higher palsy risk 5

Multiple Tumours:

• Staged procedures recommended - avoid simultaneous bilateral surgery to prevent bilateral facial nerve palsy 5
• Increased risk of temporary facial nerve palsy (19.7% overall, 0% permanent) 5

Extraparotid Sites:

• Submandibular lesions: surgical excision of the mass 4
• Large laryngeal lesions with extralaryngeal extension: open external approach for complete resection 3

Critical Surgical Principles:

Capsule rupture during surgery does NOT lead to recurrence - zero recurrence observed even with intraoperative capsule rupture 5

No adjuvant radiotherapy is indicated for completely excised Warthin tumour, unlike malignant salivary gland tumours where postoperative radiotherapy is standard for incomplete resection 6

Intraoperative frozen section may be used to confirm benign diagnosis and guide extent of resection 6

Prognosis and Follow-up

Outcomes:

• Excellent prognosis with complete surgical excision 5
• Zero recurrence rate reported in surgical series with appropriate technique 5
• No malignant transformation documented 1
• Temporary facial nerve palsy in 19.7%, permanent palsy in 0% 5

Surveillance Considerations:

• Monitor for contralateral development given 5-14% bilateral occurrence rate 1
• Screen for multicentric disease (12-20% risk) 1
• Clinical follow-up sufficient - no intensive imaging surveillance required unlike malignant tumours 5

Key Differentiating Features from Malignant Salivary Gland Tumours

Clinical Red Flags for Malignancy (ABSENT in Warthin Tumour):

• Facial nerve paralysis 6, 7
• Trismus 6, 7
• Cutaneous infiltration 6, 7
• Rapid growth 7
• Pain 7
• Fixed, hard mass 7

Treatment Differences:

Warthin tumour requires only enucleation or limited resection 5, whereas malignant salivary gland tumours require:

• Complete gland excision for major gland tumours 6
• Routine postoperative radiotherapy for stage II-IV high-grade or incomplete resection 6
• Neck dissection for T2 high-grade tumours or node-positive disease 6

Common Pitfalls and Caveats

Diagnostic Pitfalls:

• Do not misinterpret submandibular Warthin tumour as arising from the parotid tail - this affects surgical planning 4
• Laryngeal Warthin tumour may mimic mucoepidermoid carcinoma - careful pathological evaluation essential 3
• False-negative FNAB rates up to 20% - correlate with clinical and imaging findings 6, 8

Surgical Pitfalls:

• Avoid bilateral simultaneous surgery for bilateral tumours to prevent bilateral facial nerve palsy 5
• Exercise extra caution with deep lobe or multiple tumours - higher nerve palsy risk 5
• Do not perform radical surgery based solely on indeterminate frozen section - major harm decisions require definitive diagnosis 6

Management Errors to Avoid:

• Do not treat as malignancy - Warthin tumour does not require extensive resection or adjuvant therapy 5
• Do not ignore smoking history - strong etiological association guides counseling 2
• Do not dismiss possibility of coexistent pleomorphic adenoma - reported in same or contralateral gland 2