Salivary Gland Pathology Notes

Common Salivary Gland Pathologies

1. Sialolithiasis

  • Etiology:

    • Formation of calculi (sialoliths) inside the ducts or parenchyma of salivary glands.

    • Most common in the submandibular gland (SMG) and its ducts (80-90% of cases), with the remaining cases in the parotid duct.

    • Most common disease of salivary glands, accounting for 50% of major salivary pathology.

    • Due to increased viscosity of secretions from the SMG.

    • Typically occurs in adults aged 30-60 years, with a prevalence in males.

  • Clinical Presentation:

    • History of recurrent swelling and pain in the affected gland.

    • Patients usually complain of pain and swelling associated with eating due to obstruction of the draining duct, which slows or inhibits saliva flow.

  • Ultrasound Appearance:

    • Ductal ectasia and dilatation.

    • Stones can often be seen as hyperechoic foci with acoustic shadowing. Small stones (<2mm) may not shadow.

    • The gland can also appear enlarged if obstructed.

2. Sjogren's Syndrome

  • Etiology:

    • Second most common autoimmune disorder other than rheumatoid arthritis.

    • Chronic disorder involving salivary and lacrimal glands.

    • Results from hyperactivity of B-lymphocytes and autoantibody and immune complex production.

    • Affects mainly women over 40 years.

  • Clinical Presentation:

    • Dry mouth and eyes.

    • Parotid gland enlargement.

  • Ultrasound Appearance:

    • Heterogeneous gland.

    • Often contains small, round, anechoic or hypoechoic foci, resembling a “honeycomb” appearance.

    • Early stage: gland can be enlarged; late stage: gland can be atrophic.

3. Sialadenitis

  • Etiology:

    • Ranges between acute or chronic sialadenitis.

    • Can be viral or bacterial in nature.

    • Sialolithiasis is commonly present, causing obstruction with stones found in 85% of SMG ducts and 15% in parotid ducts.

    • Can be caused by dehydration and immunosuppression or drug-induced factors, but this is less common.

    • Mumps (Parotitis - another inflammatory condition) is common in children and is usually bilateral.

  • Clinical Presentation:

    • Painful swelling of the affected salivary gland.

    • Pain and swelling can be worse after eating.

    • If bacterial sialadenitis, there may be a purulent discharge.

  • Ultrasound Appearance:

    • Gland is enlarged and overall hypoechoic.

    • Can have a “spongy” appearance caused by oedema.

    • Increase in vascularity.

    • Ducts aren’t primarily affected but can have dilatation, especially if there is a stone.

    • If the infection is viral, the gland may appear normal with only the indication of multiple enlarged lymph nodes within the gland parenchyma.

4. Abscess

  • Etiology:

    • Can form as a complication from acute sialadenitis.

    • Can be due to obstruction by a stone or fibrosis.

  • Clinical Presentation:

    • Painful swelling.

    • Redness.

  • Ultrasound Presentation:

    • Hypoechoic/anechoic lesions.

    • Posterior acoustic enhancement.

    • Poorly differentiated margins.

    • Can have mobile debris within.

    • Can have hyperechoic foci – gas bubbles.

    • Increased vascularity.

5. Pleomorphic Adenoma

  • Etiology:

    • Most common benign salivary gland tumor (accounts for 70-80% of benign tumors).

    • Majority occur in the parotid gland.

    • Affects mainly middle-aged individuals with a slightly higher incidence in females (2:1).

  • Clinical Presentation:

    • Patients typically present with a smooth, painless, enlarging mass.

    • Can be asymptomatic.

    • Can undergo malignant transformation after decades if left untreated.

  • Ultrasound Presentation:

    • Typically hypoechoic, solid.

    • May show posterior enhancement.

    • Well-defined, can be lobulated.

    • Usually minimal or no vascularity.

6. Warthins Tumour

  • Etiology:

    • 2nd most common benign parotid tumour after pleomorphic adenoma.

    • Originates from the lymphoid system.

    • Occurs typically in older age group (60 years +).

    • More common in males (2:1).

    • Can be bilateral or multifocal.

  • Clinical Presentation:

    • Painless parotid swelling.

  • Ultrasound Presentation:

    • Most are oval, hypoechoic, well-defined.

    • Often contain multiple anechoic areas.

    • Often are hypervascular.

7. Mucoepidermoid Carcinoma

  • Etiology:

    • Most common in middle age groups (35-65 years).

    • Most common malignant salivary gland tumour in childhood.

    • Most common malignant primary parotid gland tumour.

    • Slightly more common in females.

  • Clinical Presentation:

    • Presents as painless swelling with or without facial nerve involvement, as most arise from the parotid gland, but can arise from any of the salivary glands.

  • Ultrasound Presentation:

    • Typically well-circumscribed hypoechoic lesion.

    • Can have a partial or completely cystic appearance.

    • Can mimic the appearance of a benign lesion.

8. Adenoid Cystic Carcinoma

  • Etiology:

    • Second most common (although still rare) malignant tumour of salivary glands.

    • Most common in middle age (40-60 years).

    • Slightly more common in women than men.

  • Clinical Presentation:

    • May include facial pain, drooping, or numbness in the lip or other areas of the face.

  • Ultrasound Appearance:

    • Low grade: well-defined, often mimicking a benign tumour.

    • High grade: infiltrative, with malignant features described as follows.

Malignant Neoplasm Features (General)

  • Irregular shape/borders.

  • Blurred margins.

  • Hypoechoic heterogeneous parenchyma.

  • Increased vascularity is common but not always present.

Metastases

  • Uncommon to be in salivary glands.

  • If present, usually from the head and neck region.

  • Can present on ultrasound as being well-defined and oval – difficult to differentiate from Sjogren’s syndrome.