Warthin tumour: A benign multifocal parotid tumour

Clinical History

A 50-year-old male smoker presented with insidious onset of bilateral infra-aural neck swellings, initially on the left side, followed by right side; painless and gradually increasing in size over a period of 2 years. On palpation, both parotid glands were enlarged with nodularity. There was no regional or generalised lymphadenopathy..

Imaging Findings

Initial ultrasonologic evaluation (images not shown) showed well defined mass lesions in both parotid glands, with few cystic areas within. CT scan of the neck revealed enlarged bilateral parotid glands, with multiple sharply marginated enhancing lesions varying in size. Few of them showed non-enhancing cystic areas within. No enlarged regional or cervical lymph nodes were noted.
Bilateral superficial parotidectomy was done. Histopathology of the resected specimen revealed multicentric tumours composed of cystically dilated spaces, glands and papillae lined by two layers of oncocytic cells. Stroma showed dense lymphoid infiltrate.

Discussion

Warthin tumour, also known as papillary cystadenoma lymphomatosum is the second most common benign tumour of the parotid after pleomorphic adenoma [1, 2]. It occurs in the 6th – 7th decade and is strongly associated with smoking. Smokers have 8 times higher risk of developing this tumour. Retrograde flow of substances in tobacco smoke into the salivary ducts or excretion of substances from smoke into the ducts is theorised as a causative factor [1].
Warthin tumour is the most common salivary gland tumour with multicentric occurrence [2] and has the greatest tendency to undergo cystic change than any other salivary gland tumour [3]. It occurs most commonly within the parotid gland, in the inferior pole [1, 2, 4]. Rarely, they occur in the cervical lymph nodes and submandibular gland [1].
The parotid gland undergoes late encapsulation in the 2nd trimester and hence incorporates lymphatic tissue, whereas other salivary glands do not and it is within this lymphoid tissue that Warthin tumour arises from [4].
Most patients are asymptomatic. Others may have pain, a growing mass, pressure symptoms or parotitis [1].
On histopathology they contain cystic spaces lined by papillary projections of bilayered oncocytic epithelium and a dense lymphoid stroma [1, 2].
On CT, they appear as multiple smoothly marginated ovoid tumours of 2-4cm in size [1, 2]. They show strong enhancement at early phase, with decreased enhancement at delayed phase scanning, whereas pleomorphic adenoma and malignant tumours show more of delayed phase enhancement. Cystic areas of low attenuation may be seen in the tumor [3, 6].
On T1 weighted MRI, like most parotid tumours they appear hypointense and well delineated from the fatty signal of the surrounding gland. On T2 weighted images unlike most benign tumours which are hyperintense, Warthin tumour shows intermediate, low or mixed signal intensity [4]. On dynamic contrast MR imaging, Warthin tumour generally shows peak enhancement in the early phase after injection of contrast bolus and rapid washout, while pleomorphic adenomas and malignant tumours show peak signal intensity in the later phase [3, 7, 8].
At nuclear scintigraphy, these tumours are unique and show increased radiotracer uptake on technetium pertechnetate scanning [4].
Warthin tumour is a benign tumour with low malignant potential. Malignant transformation occurs only in about 0.3%. Simple observation, local excision or even superficial parotidectomy is variously recommended. Local recurrence can occur in about 1.8- 2 % after local excision, and may be more because of their multicentricity [1].

Differential Diagnosis List

Final Diagnosis

Bilateral Warthin tumour of parotid glands

URL:	https://www.eurorad.org/case/11031
DOI:	10.1594/EURORAD/CASE.11031
ISSN:	1563-4086