few examples include pleomorphic adenoma , warthin 's tumor , mucoepidermoid carcinoma , low grade papillary cystadenocarcinoma , and metastatic squamous cell carcinoma . non - neoplastic cysts are a rarity and comprise 2 - 5% of all salivary gland lesions . benign cysts are classified as lymphoepithelial cyst , salivary duct cyst , and dysgenetic cyst . although literature reveals that most of the cases reported are of acquired origin , duct obstruction often seems to be the cause of the lesion . a 63-year - old male patient , presented with a swelling in front of the left ear that had persisted for 4 months . [ figure 1 ] , a single , well - defined , localized , oval shaped swelling was present in the left preauricular region , measuring approximately 3  4 cm in size . on palpation , it was non - tender , mobile , fluctuant , and soft in consistency anteriorly and firm posteriorly . ultrasonography of the left preauricular region [ figure 2 ] revealed a well - defined anechoic area measuring 3.3  1.9  3 cm seen in the superficial part of the left parotid gland . fine needle aspiration yielded a clear straw colored fluid , which had a protein content of 4.6 g / dl . magnetic resonance imaging ( mri ) , following aspiration , revealed a well - defined cystic lesion seen in the superficial part of the left parotid gland on t1 and t2 weighted sequences measuring 3.5  2.0  3.2 cm . [ figure 3 ] . a hypointense lesion with a focus of hyperintensity within the lesion a similar focus of hypointensity was seen within the lesion in gradient and t2-weighted images [ figure 3 ] . this indicated that there was hemorrhage within the lesion , which could have been caused by the aspiration . t2 weighted sequence with fat saturation and short tau inversion recovery ( stir ) images revealed an area of high signal intensity within the left parotid gland . there were occasional lymphoid follicles and normal salivary gland tissue in the surrounding connective tissue . patient was reviewed after 6 months and there was no evidence of recurrence [ figure 6 ] . extra - oral frontal view of a 63-year - old male patient , shows facial asymmetry , with a single swelling present in the left parotid region ( arrowhead ) . extra - oral clinical view of the left side of the face , reveals a single , well - defined , oval shaped swelling , approximately 3  4 cm in size , present anterior to the ear ( arrowhead ) . ultrasonographic image longitudinal view of the left preauricular region shows a well - defined anechoic area measuring 3.3  1.9  3 cm seen in the superficial part of the left parotid gland . magnetic resonance imaging : t1-weighted axial image shows a hypointense lesion within the left parotid gland ( arrowhead ) , with a focus of hyperintensity within the lesion . magnetic resonance imaging : t2-weighted axial image , shows a well - defined cystic lesion of high signal intensity , approximately measuring 3.5  2.0  3.2 cm , present within the left parotid gland ( arrowhead ) . hematoxylin and eosin stained specimen at 20 view shows the cyst wall with oncocytic metaplasia ( arrowhead ) . postoperative extra - oral clinical view of the left side of the face shows absence of the swelling in the preauricular region ( arrowhead ) . salivary duct cysts are true cysts and are also referred to as mucus retention cyst , mucus duct cyst , sialocyst , and simple cyst . according to european and american literature , salivary duct cysts constitute 10% of all cysts of the salivary glands . they may be of congenital or acquired origin . however , a vast majority of the cases are acquired and occur following obstruction in the duct . although the exact causative factor leading to obstruction is often unknown , some suggestions include calculi , mucus plugs , postoperative , or post - inflammatory strictures . salivary duct cysts most commonly involve the minor salivary glands and those in the floor of the mouth , buccal mucosa , and lip are usually involved . they rarely involve the major salivary glands and when they do , they may be multiple and are often found in the superficial lobe of the parotid . children to older adults are affected , mostly those over 30 - 40 years of age . salivary duct cyst of the parotid gland mostly presents as an asymptomatic , unilateral swelling . the cysts range from 0.8 cm to 10 cm in size but majority reach 1 - 3 cms in size . imaging plays an important role in investigation of salivary duct cysts in delineating the borders , extent of involvement , and the content . ultrasonography reveals a well - defined lesion with imperceptible walls , anechoic center , and posterior acoustic enhancement . there is no internal blood flow on power doppler or with color doppler . on computed tomography , cystic lesions appear as well circumscribed , non - enhancing ( following contrast administration ) , and low density areas . no enhancement is seen , following administration of gadolinium contrast , unlike benign mixed tumors . sialography permits only indirect visualization of the cyst , evaluated by the displacement of the ducts around them . these lesions are mostly unilocular , lined by ductal epithelium , which may be cuboidal or columnar , and completely or partly lined by squamous epithelium . occasionally , oncocytic metaplasia ( often seen in cases following ductal obstruction ) is seen . the lesions composed of oncocytic cells range from oncocytic metaplasia , and hyperplasia to benign and malignant neoplasms , including oncocytomas and oncocytic carcinomas . presence of epithelial alterations , such as metaplasias and focal papillary proliferations observed , are comparable to similar changes seen in odontogenic cysts and may be early marker of tumor manifestation . there have been rare instances of development of benign and malignant neoplasms such as adenocarcinoma and mucoepidermoid carcinoma from the lining of a salivary duct cyst . an association of latent epstein - barr virus infection with this neoplastic transformation has also been reported . surgical excision is curative . partial or total removal of the gland may be necessary . the inconspicuous clinical presentation and similarities between the epithelial linings of various lesions makes meticulous investigation mandatory . imaging plays a significant role in diagnosing parotid gland duct cyst and ultrasound should be the first modality in its screening .
non - neoplastic cysts of the salivary glands are uncommon and represent 2 - 5% of all salivary gland lesions . 
 they are mainly mucoceles or salivary duct cysts . unlike a mucocele , which is surrounded by granulation tissue 
 , the salivary duct cyst is lined by epithelium . 
 salivary duct cysts are more common in the oral minor salivary glands and rarely occur in the major salivary glands , show a marked predilection for the superficial lobe of the parotid , and represent 10% of all salivary gland cysts . 
 neoplastic differentiation of the lining of the salivary duct cyst has been reported . 
 we report a case of a salivary duct cyst of the left parotid gland , with a review of radiographic and histopathologic features .