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Salivary Gland Tumors

 

 

Related narrative: Parotid Pleomorphic Adenoma

Salivary gland tumors are uncommon (2% of all tumors, 5% of head and neck tumors). The greatest number (70%) arise in the parotid and most (90%) are of epithelial derivation. The majority are benign (80% of parotid, 60% submandibular, 50% minor and 10% sublingual). The larger the gland, the greater the chance the tumor is benign. Three quarters of parotid masses are neoplastic, the rest benign (cystic, inflammatory, granulomatous, AID's related). Most salivary gland tumors occur in adults (over 16 years of age) in the 5th and 6th decades. Malignant lesions tend to affect an older population. Most tumors (90%) present as a painless, asymptomatic mobile 4-6cm mass. Rapid growth and facial nerve involvement suggests malignancy.

The two most common benign salivary lesions are pleomorphic adenoma (55% of all salivary tumors), and Warthin's tumor (8%). Pleomorphic adenomas (see also submaxillary gland tumor), also called mixed tumors, contain epithelial derived tissues with varying degrees of mesenchymal differentiation. As they grow, they compress a partial pseudocapsule around them. There may be microscopic papillary extensions into surrounding parotid which lead to a high recurrence rate (30-50%) if not excised with a margin of gland. They are most often located in the superficial lobe of the parotid. Rarely, a pleomorphic adenoma may undergo malignant degeneration, especially if it has been present for a long period (2% @ 5 yrs, 10% @ 15 yrs). Malignant pleomorphic adenoma is highly aggressive and lethal (30-50% 5 yr mort.). Warthin's tumor (papillary cystadenoma lymphomatosum) is comprised of epithelial lined cystic spaces in a dense lymphoid stroma. Ten percent may be multifocal or bilateral. Enucleation is adequate treatment.

Mucoepidermoid carcinoma is the most common salivary malignancy and may be high or low grade. Acinic cell cacarcinoma is the next most common. Acinic cell is low grade, with a 70% 10 yr survival. Adenoid cystic carcinoma, slightly less common than acinic is high grade, tends to invade nerves and spread to the lungs. It is not possible to differentiate benign from malignant parotid lesions on clinical grounds. Fine needle aspiration (FNA) has a 95% daignostic accuracy rate and is used rather than incisional biopsy which could damage the facial nerve and spread tumor cells. Skin cancer (melanoma, squamous) of the scalp and face not uncommonly metastasize to the parotid, and the tail of the parotid is resected as part of radical neck dissection (see squamous cell carcinoma of the scalp) for these lesions.

There is a 10% incidence of transient facial nerve paresis, and a 2% incidence of permanent injury from surgery. Up to 40% of patients develop some degree of Frey's syndrome (gustatory sweating) from regenerating parasympathetic fibers reaching swear glands in the overlying skin. Various types of tissue interposition help prevent the problem.

References:

Cotran: Robbins Pathologic Basis of Disease, Sixth Edition, Copyright 1999 W. B. Saunders Company: 769-773.

Sabiston: Textbook of Surgery, 15th ed., Copyright 1997 W. B. Saunders Company: 1322-1324.

Benign salivary gland neoplasms.
Califano J - Otolaryngol Clin North Am - 1999 Oct; 32(5): 861-73

The surgical pathology of salivary gland neoplasms.
Westra WH - Otolaryngol Clin North Am - 1999 Oct; 32(5): 919-43.

Postparotidectomy facial nerve paralysis: possible etiologic factors and results with routine facial nerve monitoring.
Dulguerov P et. al., The Laryngoscope, 1999 May; 109:754-762.

Platysma muscle-cervical fascia-stermocleidomastoid muscle (PCS) flap for parotidectomy.
Yun Kim S, Mathog RS, Head and Neck, 1999 Aug; 428-433.


This page was last modified on 17-Jan-2001.