Benign Salivary Gland Tumors

Pleomorphic adenoma

The benign mixed cell or pleomorphic adenoma comprises about 80% of parotid neoplasms, representing the most common salivary gland neoplasm. They are usually solid, rounded, well defined masses, most commonly found in the superficial lobe of the parotid. On T1 weighted images, they tend to be low signal relative to the gland, and they are generally high signal on T2 weighted images. There may be some fluid containing spaces within the tumor. Unlike a typical cyst, however, they tend to contrast enhance rather brightly with some heterogeneity. There may be calcification within the tumor. A small number can degenerate into carcinomas.

Pleomorphic adenomas can arise from the deep lobe of the parotid and extend into the parapharyngeal space with an epicenter away from the parotid, but well centered in the parapharyngeal space. At times, these lesions can be difficult to differentiate from other parapharyngeal/carotid space lesions such as schwannomas and glomus tumors. However, lesions that arise from the parotid tend to have a prestyloid location. They are separated from the carotid space by the tensor palattini veli fascia. Therefore, a mass extending into the parapharyngeal space that is of parotid origin will push the carotid artery and jugular vein posteriorly, whereas those that push the carotid anteriorly are more likely to be a schwannoma or glomus tumor.

Warthin's tumor

Warthin's tumors are often bilateral and multicentric. Their imaging features resemble a pleomorphic adenoma in that they tend to have sharp borders. They also enhance with contrast, however, more centrally and less peripherally. They tend to be more common in males. They are not infiltrative and are usually limited to the gland.

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