Warthin tumours, the second most common benign tumour of the salivary glands, occur predominantly in older males who smoke, characterised by oncocytic epithelium and dense lymphoid stroma histologically, and typically appear as well-defined, cystic or solid masses with heterogeneous enhancement on imaging, predominantly in the tail of the parotid gland.
Description
Warthin tumour, also known as papillary cystadenoma lymphomatosum, is a benign salivary gland neoplasm characterised by cystic spaces surrounded by two layers of benign epithelial cells and dense lymphoid stroma. It almost exclusively occurs in the parotid gland and is the second most common benign parotid gland tumour after pleomorphic adenoma.
Pathogenesis
The exact cause is unknown, but there is a strong association with smoking. In fact, smokers are estimated to be 8 times more likely to develop Warthin tumours than non-smokers.
Epidemiology, Risk Factors & Associations
- More common in males than in females
- Typically presents in the 6th to 7th decade
- Strong association with smoking (8 times more likely in smokers)
- Possible association with radiation exposure, Epstein-Barr virus, autoimmune disorders
- Comprises 10% of parotid gland tumours.
Clinical Features
- Usually presents as a slow-growing, painless mass at the angle of the mandible
- Usually soft and fluctuant, often waxing and waning in size.
- It may be bilateral or multicentric in 5-14% of cases
- Rarely undergoes malignant transformation
Pathological Features
Histopathology
- Gross: Well-circumscribed, encapsulated, and often have a cystic nature. They can range from yellow to tan in appearance and can be filled with thick, cloudy fluid.
- Microscopic: Composed of two layers of cells, oncocytic epithelial cells and a lymphoid stroma. Cystic spaces are present with palisading oncocytic tumour cells.
Radiological Features
General Features
- Well-defined ovoid solid/cystic mass with characteristic heterogenous parenchyma, typically in parotid tail, superficial to the angle of mandible
- 20% are multifocal (may be synchronous or metachronous)
- Rarely seen in submandibular or minor salivary glands
- Can undergo cystic change
- Mural nodule strongly suggestive
- No calcification
US
- B-mode: Heterogeneous, predominantly hypoechoic mass with internal echogenic foci due to cystic changes
- Doppler: Prominent hilar and septal vessels may be seen.
CT
- Non-contrast: Well-defined, encapsulated mass that can range from iso- to hypodense relative to the adjacent muscle. Cystic component with multiple septa may be seen.
- Post-contrast: Minimal enhancement of solid components, septa and walls.
MRI
- T1: Isointense to hypointense signal in both cystic and solid components. High intracystic signal suggests proteinaceous debris or haemorrhage.
- T2: Hyperintense cystic component. Low to intermediate signal in solid component.
- DWI: ADC values lower than pleomorphic adenoma.
- T1 Gd+: Minimal enhancement of solid components, septa and walls.
NM
- FDG PET/Tc99-pertechnetate/thallium: Usually shows uptake
Grading and Staging
As Warthin tumour is a benign condition, traditional cancer staging does not apply.
Diagnosis
Fine needle aspiration (FNA) can be used for initial diagnosis and typically shows oncocytic cells, lymphoid cells, and cyst macrophages.
Differential Diagnosis
- Pleomorphic adenoma: More common, occurs in females more often, rarely bilateral. Also appears as a well-circumscribed, intraparotid mass which can be heterogenous when large.
- Mucoepidermoid carcinoma: More likely to be painful due to propensity to invade, may have nerve involvement (e.g. facial nerve weakness). Adjacent malignant nodes is common.
- Beningn lymphoepithelial lesions: Seen in HIV. Presence of tonsillar hyperplasia and cervical lymphadenopathy favours BLL.
- Non-Hodgkins lymphoma: Multiple solid, uniformly enhancing, intraparotid lesions. Presence of cervical lymphadenopathy favours NHL.
Management
Surgical excision is the mainstay of treatment for symptomatic lesions. Care must be taken not to injure the facial nerve. In some cases, conservative management may be considered if the lesion is asymptomatic, especially in older patients due to the low risk of malignant transformation.