الفهرس 
Histology of the Major Salivary GlandsOnly 14 pages are availabe for public view
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Abstract
The salivary glands are located around the mouth. The salivary glands are divided into major and minor salivary gland categories. The major salivary glands are the parotid, the submandibular and the sublingual glands. The minor glands are dispersed through out the upper aerodigestive submucosa (i.e: palate, lip, pharynx, nasopharynx, larynx, parapharyngeal space).
Tumors of the salivary glands are uncommon and represent 2-4% of head and neck neoplasms. The incidence of salivary gland neoplasms as a whole is approximately 1.5 cases per 100,000 individuals. About 75% to 80% of salivary gland tumors are benign. The frequency of benign salivary gland tumors varies by site. About 85% of parotid, 60% of submandibular, 50% of minor glands and only 10% of sublingual lesions are benign. Furthermore, in the tongue and retromolar area lesions are very rare. In the lips, 70% of tumors are benign. Benign salivary gland tumors occure most commonly in the 4th decade of life and more frequently in women than men.
Most salivary gland neoplasms (95 per cent) occur in adults. The most common benign pediatric salivary gland tumor is the hemangioma, followed by the pleomorphic adenoma.
Etiologic factors for salivary gland neoplasms are not well understood. In addition, tobacco use and alcohol consumption has not been associated with any increased incidence of salivary gland neoplasms. The Epstein-Barr Virus and Low-dose radiation has been studied as a risk factor for the development of salivary gland neoplasms.
Generally speaking benign tumors are slowly growing, peak age before 40 years and usually not associated with pain. Physical examination shows firm, cystic, nodular and freely mobile mass with no facial nerve paralysis. Grossly the mass appears well capsulated and often shows cartilage. Benign tumors show no metastasis.
The most common benign salivary gland tumors is the pleomorphic adenoma (benign mixed tumor) which comprise about half of all tumors and 65% of parotid gland tumors, 40% of intraoral tumors and about 50% of those on the palate. It is also the most common minor gland lesions. Malignant transformation is possible, resulting in carcinoma mixed tumor. Pleomorphic adenomas must be excised by parotidectomy with an adequate margin of normal parotid tissue around the neoplasm to ensure complete resection. Resection is advocated because, if observed, pleomorphic adenomas invariably continue to enlarge, and may undergo malignant transformation (at a rate of approximately 5 per cent).
Warthin’s tumor is the second most common benign neoplasm of the parotid gland and accounts for 6 to 10 per cent of all parotid tumors, but is rarely found in other salivary gland sites. Most tumors are found in older men, with an increased risk for occurrence in smokers. Warthin’s tumors are often cystic, can occur multicentrically, and approximately 10 per cent occur bilaterally. These tumors rarely undergo malignant transformation and are usually treated by parotidectomy.
Oncocytomas occur almost exclusively in the parotid gland, comprise less than 1 per cent of all salivary gland neoplasms, and commonly occur in patients who are in the sixth decade of life. These tumors are solid and are removed by parotidectomy with facial nerve preservation.
Monomorphic adenomas describe a group of rare salivary gland neoplasms, including basal cell adenoma, clear cell adenoma, glycogen-rich adenoma, and other rare tumors. The most common of this group is the basal cell adenoma, which is commonly found in the minor salivary glands, followed by the parotid gland. The monomorphic adenomas are considered benign, non-aggressive neoplasms, and are treated by parotidectomy with a margin of normal tissue.
Imaging studies of the salivary glands are usually unnecessary for the assessment of small tumors within the parotid or submandibular gland. CT scanning or MRI is useful for determining the extent of large tumors, for evaluating extraglandular extension, for determining the actual depth of parotid tumors, and for discovering other tumors in one gland or in the contralateral gland. Additionally, CT scanning and MRI are helpful in distinguishing an intraparotid deep-lobe tumor from a parapharyngeal space tumor and for evaluation of cervical lymph nodes for metastasis.
Fine needle aspiration biopsy is a valuable diagnostic adjunct in evaluation of head and neck masses. Its sensitivity in distinguishing between benign and malignant salivary gland tumors is approximately 95%.
Benign tumors of the parotid gland are treated with either superficial or total parotidectomy, depending upon the location and extent of the tumor. The facial nerve should never be sacrificed during parotidectomy for benign lesions. Benign tumors arising in the submandibular gland should be treated by simple excision of the gland while benign salivary gland lesions of the palate or lip should be resected with a cuff of normal tissue and peeled off the underlying bone if necessary.