Warthin’s Tumors of Parotid Glands

Clinical History

A 54 year old man proceeded to the outpatient department of the maxillofacial surgery clinic with a painless left cervical swelling.

Imaging Findings

The swelling became perceptible two months ago and was gradually enlarged without other symptoms. Clinical examination ascertained indolent swelling of both parotids, mostly of the left. Native CT scan showed multiple bilateral parotid solid lesions, with cystic components in the larger of the lesions at the left. A two phases helical CT scan (at 30 and 120 seconds) after IV contrast administration showed a decrease in attenuation at delayed phase. Although MRI was advised for further examination, the patient refused it and the maxillofacial surgeons proceeded to resection only of the larger lesion in the left parotid. The histological findings confirmed the Warthin’s tumors initial diagnosis. The patient returned for programmed examinations with MRI and US 1 year and 2,5 years after the first examination. The following MRI and US examinations revealed enlargement of the known multiple parotid lesions and recurrence of the lesion that was resected from the left parotid.

Discussion

Warthin’s tumor is also referred to as papillary cystadenoma lymphomatosum, adenolymphona or lymphomatous adenoma. It’s the second most common benign tumor arising in the parotid gland after benign mixed tumor. Warthin’s tumor comprises 4-15% of all salivary gland epithelial tumors and 4-10% (up to 30% according to others) of all parotid tumors. 5-20% of cases appear to be multicentric. There is a peak incidence in the 5th to 7th decades and it is 3 times more frequent in men. Malignancy developing in a Warthin’s tumor is extremely rare (<1%). On Ultrasound, Warthin’s tumours appear rounded or lobulated, are well circumscribed and internal cystic changes with septations are common. On CT, Warthin’s tumors usually appear as small (2-4 cm, rare >10 cm), ovoid, smoothly marginated masses. They are homogenous soft-tissue density lesions without calcifications. Cyst formation with homogenous material (10 to 20 HU) is common (30%). The cyst wall is usually thin and fairly smooth. The presence of a mural nodule helps to distinguish Warthin’s tumors with large cystic components, septae or multiple adjacent cystic lesions from first branchial cleft cysts or lymphoepithelial cysts. In two phases CT (at 30 and 120 sec) after IV contrast material administration, usually these tumors present with a decrease in attenuation during the second phase. On MRI solid and cystic components show low T1 weighted signal, but cystic areas may show high signal secondary to proteinaceous debris and/or hemorrhage. In T1 weighted images after contrast administration solid components show minimal contrast enhancement. In T2 weighted images, solid components appear intermediate to high signal, with high signal in cystic foci, intermediate signal in Proton Density weighted images, while in STIR images the lesions become more conspicuous, especially the cystic components. Warthin's tumors show significant restriction of diffusion (high signal in DWI images and low signal in ADC maps). The mean ADC values are very low (0,81-0,96 x10-3 mm2/sec), a finding that is helpful to differentiate them (together with their morphologic characteristics) either from pleomorphic adenomas (2 x10-3 mm2/sec) or from malignant tumors (1,29-1,38 x10-3 mm2/sec). The differential diagnosis of Warthin’s tumor includes benign mixed tumor, benign adenopathy, lymphoma, benign lymphoepithelial lesions – HIV, adenoid cystic or mucoepidermoid carcinoma, as well as squamous cell carcinoma and melanoma nodal metastasis. When a benign mixed tumor is small, it is a well-circumscribed, homogenous, intraparotid mass. On the contrary the larger lesions may be inhomogeneous and mimic Warthin’s tumors. The benign lymphoepithelial lesions may strongly mimic Warthin’s tumors, when they are unilateral and singular. Tonsilar hyperplasia and cervical adenopathy may help in the differential diagnosis. Low grade parotid malignancy like adenoid cystic and mucoepidermoid carcinoma may be well demarcated, while in higher grade, more advanced parotid malignancy, the differential diagnosis is easy because of its invasive appearance on imaging. In the squamous cell carcinoma or melanoma nodal metastases, a primary malignancy can be found on or around the skin of the ear with single or multiple parotid masses with invasive margins and often with central necrosis.

Differential Diagnosis List

Final Diagnosis

Warthin’s tumors of parotid glands.

URL:	https://eurorad.org/case/4957
DOI:	10.1594/EURORAD/CASE.4957
ISSN:	1563-4086