Salivary glands may be classified as major and minor glands. Major glands are paired glands. They include parotid, submandibular and sublingual salivary glands. There are numerous minor salivary glands that are widely distributed of oral cavity of submucous layer. They include labial, buccal, palatine, lingual and incisive glands. All these glands secrete saliva, which serves as a lubricant for the food bolus and has immunologic, digestive and cleansing properties. Based on their secretions, salivary glands are classified as:
- Mucous salivary glands
- Serous salivary glands
- Mixed salivary glands.
Salivary glands are often involved in a wide variety of disorders that frequently require surgical treatment. These glands can be involved with acute and chronic inflammatory processes, give rise to benign and malignant neoplasms, manifest congenital abnormalities or represent involvement of a systemic disorder. Amongst all the disorders, the most common are problems with neoplasms and infections.
Salivary gland disorders can be broadly classified as follows:
- Developmental anomalies
- Enlargement of gland
- Tumors of salivary glands
- Necrotizing sialometaplasia
- Salivary gland dysfunction
Salivary glands are susceptible to numerous systemic and local inflammatory conditions, usually secondary to bacterial or viral infections or obstructive pathologies. Trauma to the gland or duct may also result into inflammation. Inflammation of the duct progresses through stages of edema, cellulitis and eventually obstruction. The obstructive phase causes degeneration of glandular parenchyma and fibrosis and hence may often require surgical management.1
Tumors of the salivary glands can affect both, the major and minor salivary glands. Salivary gland tumors are uncommon and 95.4% are parenchymal in origin where as 4.6% are interstitial in origin. Interstitial tumors arise from the vessels, lymph nodes and nerves. They could be either benign or malignant. Benign parenchymal salivary gland tumors include pleomorphic adenoma, Warthin's tumor, basal cell adenoma, canalicular adenoma, oxyphilic adenoma, ductal papilloma and myoepithelioma. Malignant salivary gland tumors include mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma and malignant mixed tumor. Malignant tumors can affect both minor as well as major salivary glands. In most parts of the world the incidence of benign and malignant neoplasms of the salivary glands varies from 1 to 2 per 100,000 populations per year. The majority of lesions occur in the parotid gland. The parotid gland is most commonly involved in neoplasia followed by submandibular gland, minor salivary glands and lastly the sublingual gland. The frequency of occurrence of malignant salivary gland neoplasms is parotid, 25%; submandibular gland, 25%; sublingual gland, 100%; accessory glands, 50% or more.2 Thus, parotid is the most commonly affected gland by the tumors and a tumor in the minor salivary gland is most likely to be malignant. However, in a survey carried out by Potdar GG and Paymaster JC at Tata Memorial Hospital, Mumbai during 1941 to 1965, it was found that out of 355 salivary gland tumors 110 (31%) were located in minor salivary glands.2
Until 1953, there was much confusion regarding histologic and biologic behavior of salivary gland neoplasms, which led to poor management of these neoplasms. Despite their characteristically pronounced variation in histological appearance, all salivary gland tumors were simplistically separated only into ‘infiltrating’ and ‘encapsulated’ types. Serious attempts at a clinicopathological correlation were not made until the late 1940s and early 1950s. Foote and Frazell's monograph on tumors of major salivary glands in 1953 was the first ever classification of salivary gland tumors wherein emphasis was placed on histologic classification and analysis of several tumor types under conditions in which surgical treatment was accented. They reviewed 877 cases accumulated over a period of 20 years ending in 1949.3 Refinement of clinical examination, diagnostic imaging techniques, microscopic diagnosis and immunohistochemical techniques has resulted in more precise diagnosis and treatment.
Salivary gland neoplasms, both benign and malignant, present as painless masses and hence diagnosis of these tumors is essential at an early stage to rule out possibility of a malignancy that could have a poor prognosis.
The management of salivary gland tumors chiefly includes surgical excision of the lesion with or without removal of adjoining structures depending on the histopathological diagnosis of the tumor. Radiotherapy has also been used as an adjunct in the management of high-grade malignant tumors of the salivary glands. The more aggressive surgical approach in the fifth decade of the last century could be attributed to the more precise surgery in regard to the facial nerve exposure and to a centralization of salivary gland tumor treatment in medical centers.
- Rankow RM, Polayes IM. Inflammatory disorders. Surgical Management. Diseases of Salivary glands. WB Saunders, Philadelphia. 1976;9(2):229-38.
- I Van Der Waal. Salivary gland neoplasms. I Van Der Waal, Prabhu SR, Wilson DF, Daftary DK, Johnson NW (Eds). Oral diseases in the Tropics, Oxford University Press, Delhi. 1993;41:478-86.
- Carlson ER. Salivary Gland tumors: classification, histogenesis and general considerations. Oral and Maxillofacial surgery clinics of North America. 1995;7(3):519-27.