TUMORS OF SALIVARY GLANDS: General Considerations

The annual incidence of salivary gland tumor worldwide is 1.0–6.5/100,000. That means salivary gland tumor is not a rare entity.

Parotid glands: Around 60–80% of salivary gland tumors occur in parotid gland and relatively low percentage of tumors are malignant in nature. Around 2/3rd to 3/5th parotid tumors are benign in nature. Pleomorphic adenoma is most common tumor occurring in parotid gland followed by Warthin’s tumor. 

Submandibular gland: Approximately 8–11% of salivary glands tumors occur in submandibular gland. The incidence of malignant tumor involving submandibular gland is more as compared to parotid gland. Pleomorphic tumor followed by adenoid cystic carcinoma is most common tumors of salivary gland. 

Sublingual gland: The occurrence of tumor in sublingual salivary gland is rare. However, the chances of malignant tumors are more in sublingual gland as compared to other two major salivary glands.

Minor salivary glands: Minor salivary gland tumor is the second most common site for salivary neoplasia. The frequency of malignant tumors in minor salivary gland is far more common as compared to major salivary gland tumors. 

Mucoepidermoid carcinoma is the most common malignant tumor of minor salivary gland. 

Palate is the most common site for salivary gland tumors accounting for about 50% of tumor occurring at this site. The density of minor salivary gland is more in posterolateral hard or soft palate that is why more tumors occur at posterolateral aspect of palate. 

Although CT and MRI have replaced the sialography in evaluation of salivary masses, the reader should be aware of some sialographic patterns obtained in cases of neoplasia. 

In tumors, sialography will show the following patterns: 

a. Ductal splaying or “ball in hand” appearance 
b. Ductal displacement, buckling or cut off 
c. Abrupt ductal irregularities or displacement and contrast spilling within gland 
d. Filling defects on parenchymal opacification. 

The above sialographic signs are non-specific and could not be able to differentiate between low grade malignancies and benign tumors. Sialographic pattern suggestive of malignancy is abrupt ductal irregularity and displacement and contrast spilling in tissue parenchyma.

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