Salivary Gland Infections: Causes, Types, Symptoms

Salivary Glands

Definition of Salivary Glands: it is defined as Produce Saliva (Spit) And Empty it Into Your Mouth Through Ducts, Or Small Openings.

Salivary Glands Normal Structure

Groups of Salivary Glands:

• Major salivary glands: There are three major paired salivary glands namely parotid,
  submandibular, and sublingual.
  • The main duct of the parotid gland opens into the oral cavity, opposite the second maxillary molar.
  • The ducts of submandibular and sublingual glands open into the floor of the mouth.
• Minor salivary glands: There are many minor salivary glands widely distributed throughout the mucosa of the oral cavity.

Read And Learn More: Pathology for Dental Students Notes

Histology of Salivary Glands:

1. Salivary glands:

• They are tubuloalveolar glands.
• The secretory acini may contain mucus cells, serous cells or both.
  • Parotid gland: Purely serous
  • Submandibular gland: Mixed type but is predominantly serous.
  • Sublingual gland: Mixed type but is predominantly mucus.
  • Minor salivary glands: Serous, mucus, or mixed type.

Salivary Glands Infection

2. Salivary duct: The secretory acini of major glands are drained by ducts. They are lined by:

• Low cuboidal epithelium in the intercalated portion.
• Tall columnar epithelium in the intralobular ducts.
• Simpler epithelium in the secretory ducts.

3. Saliva: Salivary glands secrete saliva.

• It acts as a lubricant during swallowing and speech, contains the enzyme amylase, and has antibacterial properties.
• The salivary gland may develop the inflammatory or neoplastic disease.

Salivary Glands Sialadenitis

• Sialadenitis is inflammation of the salivary gland.
• Types: Acute or chronic (more common).

Salivary Glands Infection

Etiology of Sialadenitis: 

It may be caused by trauma, viral or bacterial infection, or autoimmune disease.

Viral infections of Sialadenitis:

• Mumps is the most common cause of viral sialadenitis in school children. Mumps involves the major salivary glands, particularly the parotids. Mumps may also involve other glands such as testis (orchitis)/ovary (oophoritis) and pancreas (pancreatitis). Involvement of testis can result in testicular atrophy and infertility.’
•  Other: Cytomegalovirus infection is rare.

Bacterial and Fungal Infection of Sialadenitis:

Bacterial infections of the salivary gland cause acute sialadenitis and recurrent attacks of acute sialadenitis can lead to chronic sialadenitis. Nonspecific bacterial sialadenitis is common, especially in submandibular glands. It is usually secondary to ductal obstruction caused by Salivary Glands Stones (sialolithiasis).

The common organisms are S. aureus and Streptococcus viridans. The Salivary Glands Stone  formation may due to obstruction of the orifices of the salivary glands by impacted food debris or by edema about the orifice after injury.

Salivary Glands Infection

Causes of Acute Sialadenitis:

It may occur in acute infectious fevers. Decreased salivary secretions caused by dehydration may lead to the development of acute bacterial suppurative parotitis in elderly patients with a recent history of major thoracic or abdominal surgery. It is due to ascend of infection from mouth into parotid duct.

Causes of Chronic Sialadenitis:

1. Recurrent obstructive type: Recurrent obstruction of ducts due to calculi (sialolithiasis), stricture, injury, surgery etc. may cause recurrent attacks of acute sialadenitis due to
   ascending infections. These acute attacks may result in chronic sialadenitis.
2. Recurrent non-obstructive type: Decreased secretory function or reduced salivary secretion may also predispose to secondary bacterial invasion. This may occur in patients receiving drugs (for example, Antihistamines, antihypertensives, antidepressants, and phenothiazines), irradiation or congenital malformations of the duct system.
3. Chronic inflammatory diseases: For example, Tuberculosis, actinomycosis and fungal infections can rarely cause chronic sialadenitis.
4. Autoimmune diseases: Sialadenitis is observed in two autoimmune diseases
   1. • Sjögren syndrome: It is characterized by widespread inflammation of the salivary glands and the mucus-secreting glands of the mucosa which induces dry mouth (xerostomia). Concomitant involvement of the lacrimal glands in Sjögren syndrome may also produce dry eyes (keratoconjunctivitis sicca).
      • Mikulicz’s syndrome: It is characterized by inflammatory enlargement of salivary and lacrimal glands.
5. Frequently, no underlying cause can be detected.

Salivary Glands Infection

Morphology of Chronic Sialadenitis:

• Gross: Irrespective of the etiological agent, the salivary glands are swollen. Acute sialadenitis produce local redness, painful enlargement and tenderness. Th ducts opening in the mouth may show purulent discharge. Chronic sialadenitis may show fim swelling of the involved gland.
• Microscopy:
  • Acute viral sialadenitis in mumps: Swelling and vacuolation of cytoplasm of acinar epithelial cells. Interstitial edema, firinoid degeneration of collagen, and dense infitration by lymphocytes, macrophages, and plasma cells.
  • Acute bacterial sialadenitis: It is usually unilateral and involved a single gland. Whatever, the origin, the obstructive process and bacterial invasion lead to a nonspecifi inflammation of the affected glands. The inflammation may be largely interstitial. If it is caused by staphylococcal or other pyogens, it may be associated with suppurative necrosis and abscess formation.
  • Chronic and recurrent sialadenitis: Increased lymphoid tissue in the interstitium, progressive loss of secretory epithelial tissue and fibrosis at a later stage.

Salivary Glands Neoplasms

Salivary gland neoplasms are relatively uncommon.

Incidence of Neoplasms:

• Parotid gland—65% to 80% and ~ 15% to 30% of parotid tumors are malignant.
• Submandibular gland—10% and ~ 40% are malignant.
• Minor salivary glands including the sublingual glands—10%. About 50% of minor salivary gland and 70% to 90% of sublingual tumors are malignant.
• Malignancy in the salivary gland is inversely proportional to the size of the gland.

Classification of Salivary Glands Tumors:

• Classify salivary gland tumors.
  1. Age: Benign tumors occur in the fifth to seventh decades of life. The malignant tumors appear later.
  2. Sex: Slight female predominance, except for Warthin tumor, which occurs more often in males than in females.

Salivary Gland Tumors Symptoms

Salivary Gland Tumors Clinical Presentation:

• Parotid gland neoplasms produce swellings in front of and below the ear.
• Both benign and malignant tumors range in size from 4 to 6 cm in diameter.
• Most tumors are mobile except advanced malignant tumors.

Classification of tumors of the salivary glands:

Salivary Glands Pleomorphic Adenoma

Write a short note on pleomorphic adenoma.

Pleomorphic adenoma is a most common benign tumor of the salivary glands, characterized by an admixture of epithelial and stromal elements, and is also called mixed tumor.

• Age: It occurs usually during the third to fifth decade of life (middle age).
• Sex: It is most frequent in females.

Site of Pleomorphic Adenoma:

• Major salivary gland: Common site and constitute about 60% of tumors in the parotid. Usually arise in the superficial lobe of the parotid. Less common in the submandibular glands and very rare in the sublingual gland.
• Minor salivary gland: Its involvement is relatively rare.

Etiology of Pleomorphic Adenoma:

Not known. Exposure to radiation increases the risk.

• Nature: It is a benign tumor.
• Cell of origin: Histogenesis uncertain. It was called as mixed tumor, because of the mixture of epithelial and mesenchymal components. However, it is now considered that the tumor neoplastic cells (epithelial and those which appear mesenchymal), are of either myoepithelial or ductal reserve cell origin.

Salivary Gland Tumors Symptoms

Morphology of Pleomorphic Adenoma:

Write a short note on gross and microscopy of pleomorphic adenoma.

1. Gross of Pleomorphic Adenoma

• Shape: Round
• Size: Ranges from 2.5 to 6 cm in diameter.
• Consistency: It depends on the relative amount of epithelial cells and stroma. Usually rubbery, resilient mass with a bosselated surface.
• Well-circumscribed/capsulated: In some, the capsule is not fully developed, and small extensions can be seen protruding into the surrounding salivary gland. This makes the enucleation of the tumor difficult.
• Cut surface: It shows gray-white with myxoid and blue glistening, translucent chondroid (cartilagelike).

2. Microscopy of Pleomorphic Adenoma:Characteristic feature is the pleomorphic appearance. Neoplastic cells show varying mixtures of epithelial tissue components intermingled with cells showing mesenchymal differentiation.

• Epithelial element: This component consists of ductal cells and myoepithelial cells.
• Epithelial elements are arranged in the form of ducts, acini, and irregular tubules. The ducts are lined by both epithelial (cuboidal to columnar) cells and surrounded by myoepithelial components (a layer of deeply chromatic, small myoepithelial cells).
• May show strands or sheets of plasmacytoid or spindled myoepithelial cells.
• Islands of well-differentiated squamous epithelium may also be seen.
• Mesenchymal-like elements: The epithelial elements are dispersed within a varying amount of mesenchyme-like background of loose myxoid tissue, isla

Clinical Features of Pleomorphic Adenoma:

• Pleomorphic adenomas present as painless, slow-growing, mobile, discrete tumors in the parotid or submandibular areas or in the buccal cavity.
• The tumors tend to protrude focally from the main tumor into adjacent tissues.
• Failure to recognize these minute protrusions at surgery is responsible for the recurrence of these tumors.

Carcinoma Ex Pleomorphic Adenoma:

• Rarely, a carcinoma may arise in pleomorphic adenomas—referred to as a carcinoma ex pleomorphic adenoma or a malignant mixed tumor. The incidence of carcinoma increases with the duration of the tumor.
• Microscopy: These tumors show poorly differentiated adenocarcinoma or undifferentiated carcinoma in an otherwise benign pleomorphic adenoma.

Salivary Glands Warthin Tumor

Write a short note on Warthin Tumor.

Warthin tumor (papillary cystadenoma lymphomatosis, adenolymphoma) is a benign and the second most common salivary gland neoplasm.

• Site: It almost exclusively arises in the parotid gland.
• Sex: It is the only salivary gland tumor that is more common in males than in females.
• Age: It usually occurs between the fifth to seventh decades of life.
• Predisposing factor: Smokers have eight times the risk of nonsmokers.

Morphology of Warthin Tumor:

• Gross:
  • Shape: It is round to oval, encapsulated masses.
  • Size: It ranges from 2 to 5 cm in diameter.
  • Usually arises in the superficial parotid gland and is readily palpable.
  • About 10% are multifocal and 10% are bilateral.
  • Cut section: It is a pale gray tumor punctuated by narrow cystic or cleft-like spaces filled with a mucinous or serous secretion or even resembles used (dark) motor oil.
• Microscopy: Tumors consist of cystic glandular spaces embedded in dense lymphoid stromal tissue.
  • Cystic spaces:
    • Cystic glandular spaces show papillary or polypoid projections.
    • Cystic spaces are lined by a distinctive double layer of neoplastic epithelial cells consisting of:
      • Surface superficial layer of columnar cells with abundant, finely granular, eosinophilic cytoplasm (oncocytes). Oncocytes have abundant mitochondria → responsible for the
        granular appearance to the cytoplasm.
      • The second layer below the superficial layer consists of cuboidal to polygonal cells.
  • Lymphoid stromal tissue: Cystic spaces are embedded in a dense lymphoid stroma that closely resembles a normal lymph node. The lymphoid tissue is prominent with germinal centers and is composed of B and a few T cells.
• Histogenesis: Warthin tumor may represent an aberrant incorporation of lymphoid tissue in the parotids.
• Behavior: It is benign, and about 2% may recur.

Mucoepidermoid Carcinoma

Most common primary malignant tumor of the salivary glands.

Incidence of Carcinoma:

• Constitute about 15% of all salivary gland tumors.
• Occur mainly (60–70%) in the parotids.
• Account for a major fraction of the minor salivary gland tumors.

Etiology of Carcinoma:

In about one-third of cases, it is associated with a distinctive balanced (11;19) (q21;p13) chromosomal translocation. This creates a fusion gene composed of portions of the CRTC1 (formerly known as MECT1) and MAML2 genes.

The translocation results in the activation of the Notch pathway.

Morphology of Carcinoma:

• Gross:
  • Size: It can grow as large as 8 cm in diameter.
  • Appear circumscribed, but do not show well-defined capsules and are often infiltrative at the
    margins.
  • Cut section: It is pale and gray-white and frequently contains small, mucin-containing cysts.
• Microscopy: Composed of variable mixtures of:
  • Squamous cells
  • Mucus-secreting cells
  • Intermediate cells.
  • These tumor cells are arranged in cords, sheets, or cystic structures. The intermediate cells have squamous features, with small to large mucus-filled vacuoles. The mucus stains are positive with mucin stains.
  • The tumor cells may appear regular and benign or highly anaplastic and malignant.

Salivary Gland Tumors Symptoms

Grading: These tumors are graded as low, intermediate or high grade. Clinical features and prognosis depend on the grade of the neoplasm.