Parotid gland tumours

What it is

Parotid gland neoplasms are the most common salivary gland neoplasms. The benign ones are pleomorphic adenoma, which is slow growing, smooth and mobile, and Warthin tumor, which is seen in elderly males. The malignant one to name is mucoepidermoid. In short, the most common benign parotid swelling is pleomorphic adenoma and the malignant parotid swelling is mucoepidermoid.

How it presents

The usual presentation is a painless mass. A slowly enlarging mass on the side of the face located in the tail of the parotid gland, with no evidence of facial nerve involvement, is most likely a pleomorphic adenoma.

Facial nerve involvement changes the reading. The facial nerve passes via the parotid gland, so facial nerve involvement, that is facial paralysis, increases the risk of malignancy; if the patient has facial nerve paralysis this is malignancy until proven otherwise. Parotid gland tumors also sit among the secondary causes of facial nerve palsy, alongside trauma, herpes zoster, malignant otitis externa and acoustic neuroma.

How it is diagnosed

Investigations are FNA biopsy, CT, US and MRI, and FNAC should be done in a parotid swelling. Not every parotid swelling is a tumour. A diffuse parotid swelling with a dry mouth and grittiness in the eyes, without facial nerve palsy, is Sjogren's syndrome; most patients with Sjogren's present in the post menopausal years and multi-system involvement is common. Bilateral parotid gland swelling with bilateral facial nerve palsies that improves following steroid treatment is sarcoidosis, which occurs bilaterally in 70% of cases. Bilateral painful parotid enlargement in a young adult who also has pancreatitis, orchitis, reduced hearing or meningoencephalitis is viral parotitis, so suspect mumps.