eRadiograph Volume 7: Imaging of Oral Cavity | Page 227

These are the most common salivary gland tumors to be bilateral and multifocal, 25%
are synchronous, 75% are multisynchronous.
These appear as well circumscribed encapsulated tumors in the posterior portion of the
superficial portion of the parotid gland. On CT they are hypodense, ON MRI they are
T1 hypointense, T2 hyperintense but may contain foci of T2 hypointensity. It is difficult
to differentiate this from a pleomorphic adenoma. Though WT doesn't demonstrate
dystrophic calcification. Malignancy developing in a WT is rare. An exophytic WT with
cystic component may mimic a branchial cleft cyst or a necrotic node. On FNAC WT
reveal a characteristic blackish aspirate. Treatment is superficial parotidectomy with
preservation of facial nerve.
Other benign lesions are - basal cell adenoma, cystadenoma, myoepithelioma,
oncocytoma.
These do not have any specific features.
Carcinomas: Carcinomas in the head and neck are predominantly squamous cell
carcinomas, however in the salivary glands they are a diverse group of nearly 20
histopathological subtypes. Similar to benign lesions a few specific features may help
determine the histopathological type but a specific diagnosis is only possible with
histopathology.

Imaging appearance depends on the grade of the tumor –Low grade tumors mimic
benign tumors with well defined smooth margins, with cystic areas and focal
calcification. High grade lesions have indistinct infiltrating margins. As these high
grade tumors are cellular they are hypo to intermediate on T1 and T2 weighted images.
High intensity foci may be seen within the masses. They demonstrate heterogenous
enhancement with gadolinium. High grade tumors may show perineurial infiltration of
the facial nerve. Complete surgical resection is the treatment of choice. If there is a
positive surgical margin–recurrence is 50% for low/intermediate grade and 80% for
high grade lesions.
Adenoid Cystic Carcinoma
This is the second most common salivary gland malignancy arising from the peripheral
parotid ducts. This is a slow growing widely infiltrative tumor with a tendency for
perineural spread accounting for 2 – 6% of parotid gland and 30% of minor salivary
gland tumors.

227

Parotid Space

MUCOEPIDERMOID CARCINOMA: Most common salivary gland malignancy – 80%
occur in the parotid. Radiation is the most common implicated factor in development
th
of these tumors (44%) generally occurs in the 5 decade but also in children.