Parotid Gland – pathology

Parotitis

Parotitis is inflammation of the parotid gland.

It may be secondary to:

  • Viral (Mumps),
  • Bacterial (may develop into an abscess),
  • Autoimmune (Sjogren’s syndrome),
  • Calculus /obstruction,

Parotitis is usually bilateral. The glands will be enlarged and heterogeneous with increased vascularity as shown below.

Parotitis extending into the accessory Parotid gland.

Marked hyperaemia confirms that this is an active process.

Sjogren’s disease

  • Is an autoimmune disorder affecting the moisture producing exocrine glands (tears and saliva). It is suggested to be the 2nd most prevalent rheumatic disorder (2nd to Rheumatoid arthritis). Symptoms can often be only nuisance value, so many cases are thus unreported.
  • Symptoms may include dryness of eyes/mouth (Sicca syndrome)
  • MALT lymphoma may occasionally develop in the parotid glands of Sjogren’s patients
The diffuse lymphadenititic nodules seen throughout the parotid in Sjogrens syndrome.

Parotid cysts

  • A benign and not uncommon finding.
  • Aspiration under ultrasound guidance if symptomatic.

Simple cysts may occur in either the Parotid or Submandibular glands.

Cysts may become complex. Mural thickenings or nodules warrant further investigation or follow-up depending on clinical presentation.

Any internal vascularity of the mural change should be treated with suspicion.

Parotid calculus and sialectasis

  • Sialectasis (or sialectasia) is the dilatation of the salivary ducts within the salivary gland.
  • This may appear as ‘cystic dilatations’  of the ducts (ectatic).

Ultrasound of ectatic parotid sialectasis (duct dilatation)

The dilated parotid duct exiting the parotid gland. Sialectasis may only be transient and present after eating or stimulating the parotid.

  • By asking the patient to hold water in their mouth and ‘puff’ it into their cheek, the distal duct can be examined. (see image below)

The calculus is easily seen in the Stensen’s duct as it exits the main body of the parotid gland heading medially.

Parotid duct calculi are less common than submandibular duct calculi..

Ultrasound of the distal parotid duct (green) and ampulla. Water (blue) has been used as a contrast and to expel oral air, by asking the patient to squeeze a mouthful into their cheek

Parotid Neoplasms

Ultrasound is a very useful tool to investigate parotid pathology. In the case of neoplasms, the role of ultrasound is to accurately differentiate malignant from benign is widely disputed. 

In any case of a parotid lesion, FNA or biopsy should be considered, as features of both often overlap. 

Parotid adenoma / adenocarcinoma

  • Adenomas are more common than adenocarcinomas.
  • Incidence of adenocarcinoma is approximately 1:100,000 with a 70% 5yr survival. (ref: cancer.net)

NB: ultrasound cannot distinguish between the two.

There is an increased risk of adenocarcinoma in patients who have undergone head/neck radiation treatments.

Adenomas of the salivary glands are usually hypoechoic, well-circumscribed and have posterior enhancement. An adenocarcinoma cannot be excluded on ultrasound criteria alone.

Internal vascularity confirms a solid mass versus a complex cystic lesion.

NB: Absence of seeing flow on colour doppler does not exclude a solid tumor. It simply means that now flow was detected/discernable on colour doppler.

Pleomorphic adenoma

B-mode and colour Doppler image of a pleomorphic adenoma.

An ovoid, well-circumscribed hypoechoic and vascular mass containing cystic spaces. 

Images courtesy of Callum Linehan. 

B-mode and colour Doppler image of a pleomorphic adenoma. A case of a solid inhomogenous lobulated hypoechoic lesion containing vascularity.  

Images courtesy of Callum Linehan. 

Ultrasound image of a pleomorphic adenoma. A large heterogenous vascular mass, note the margins are still well circumscribed.  

Images courtesy of Callum Linehan. 

Colour Doppler image demonstrating internal vascularity. 

Warthin’s tumour

B-mode and colour Doppler image of a Whartin’s tumour. Often presents as a well-circumscribed partially cystic mass. The solid component is heterogenous and vascular. 

Image courtesy of Callum Linehan. 

Transverse B-mode and colour Doppler ultrasound image of a Whartin’s tumour.

Appearances do vary greatly and FNA / biopsy is needed to differentiate parotid tumours. 

Image courtesy of Callum Linehan. 

Acini cell carcinoma

Ultrasound image – Acini cell carcinoma of the parotid gland with colour Doppler. Presents as a lobulated, hypoechoic and vascular mass containing calcification. 

Images courtesy of Callum Linehan. 

Ultrasound image – Acini cell carcinoma of the parotid gland demonstrating calcification. 

Image courtesy of Callum Linehan. 

Squamous cell carcinoma (SCC)

B-mode and colour Doppler image of primary parotid gland squamous cell carcinoma (SCC). 

A lobulated hypoechoic and vascular mass with cystic degeneration.

Images courtesy of Callum Linehan. 

Ultrasound image of distant cervical chain metastasis from the parotid SCC. 

In cases of any salivary gland lesion, regional lymph nodes should be assessed for metastasis. 

Images courtesy of Callum Linehan. 

Ultrasound image – Primary parotid SCC. 

A solid hypoechoic lobulated mass infiltrates the adjacent SCM muscle and parotid gland. 

Images courtesy of Callum Linehan. 

Colour Doppler image – Parotid SCC. 

Demonstrates some internal vascularity. 

Ultrasound image – Primary parotid SCC. 

A solid hypoechoic mass with ill-defined irregular margins. Note the tumour extension into the gland parenchyma (arrow).

Image courtesy of Callum Linehan. 

Ultrasound image – Primary parotid SCC. 

Contains small calcifications presenting as punctate echogenic foci (arrows).

Image courtesy of Callum Linehan. 

Parotid metastases

  • Parotid metastases whilst uncommon can occur.
  • Localised spread is more common, however  the primary may be distant from the head/neck.
  • Lymphoma should be considered if multiple lesions.

Ultrasound of an scc metastasis to the parotid. Note the complex appearance of the central necrosis and the internal vascularity confirming this is not merely a complicated cyst.

Ultrasound of a parotid mass biopsy:

  1. A fine needle biopsy.
  2. A core needle biopsy.

This was a squamous cell carcinoma metastasis.

B-mode and colour Doppler image – Multiple large metastatic melanoma deposits within the parotid gland.

4 months prior, this patient had cutaneous melanoma excised from the right cheek over the parotid gland.

On presentation, hard palpable swelling of the parotid was noted with no erythema, pain or post prandial symptoms. 

Images courtesy of Callum Linehan. 

Ultrasound image – Parotid metastatic melanoma. 

Heterogenous vascular masses with irregular margins. 

Tumour extension through the gland is seen with involvement of the adjacent intra-parotid lymph nodes.

Image courtesy of Callum Linehan. 

Ultrasound image of metastatic melanoma involving cervical chain lymph nodes.

PET imaging later revealed systemic spread resulting in stage IV melanoma. 

Image courtesy of Callum Linehan. 

Parotid atrophy

Ultrasound of the Right Parotid gland region.

The patient presented for a scan for a lump in the left parotid region. This was diagnosed as an inflammatory lymph node. Comparison with the rt side was then done (mouseover).

The appearance was initially confusing as the parotid gland could not be found. There was hypoechoic tissue that looked like fat in the space the parotid should be occupying. The diagnosis of parotid atrophy was confirmed by comparing it to a CT Brain that had been performed 12 months earlier.

The same patient had a brain CT 12months earlier.

A comparison was made after the ultrasound and it helped confirm the atrophy of the Parotid gland.

The abscent/atrophied right parotid is notable in both the coronal and axial scan planes.