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Salivary Gland Tumors

Disease State: Salivary gland tumors.

Alternative Names: Salivary gland neoplasms.

Definition: A growth arising in tissue of salivary gland origin.

What Is Going on in My Body? There are three pairs of major salivary glands. The first pair are the parotid, which sit in front of and just below the external ear and are the largest of the salivary glands. The second largest pair of glands are the submandibular glands, which sit just on the inside of the jaw in front of the angle of the mandible. Lastly, there are the pair of sublingual glands, which sit under the tongue in the front part of the floor of mouth. The parotid and submandibular glands drain through a single duct into the mouth, whereas the sublingual glands have numerous small drainage pathways. Scattered just underneath the lining of the mouth and throat are minor salivary glands. These are approximately the size of a lentil bean and drain through individual small ducts onto the lining of the mouth and throat. Salivary gland tissue also exists in the nasal cavity, larynx, and middle ear space.

The function of the salivary glands is to secrete saliva, which has a number of important functions. Amylase, an enzyme in the saliva, helps to break down complex starches and carbohydrates. Saliva is a very important material to maintain dental health. People with insufficient or abnormal forms of it tend to have more cavities. Saliva is an important lubricant to allow easy passage of swallowed material, particularly that which might be dry or scratchy. The salivary gland microscopically is composed of small structures called acini. There are a number of acini that drain into a small duct. Cells that line the duct help to modify the secretion mostly by re-absorbing some of the water content. The saliva then exits the gland through a large duct.

Salivary gland tumors can arise from any of the various cell types forming the glandular and ductile systems but also some of the supporting structures not involved in saliva secretion or transport. These growths can be benign or malignant.

What Are the Signs and Symptoms? Most salivary gland tumors arising from major glands present as gradually enlarging growths. They are often single masses. The involvement of adjacent nerves manifested as facial paralysis or pain are ominous findings and strongly suggest malignancy. Tumors arising from minor salivary glands usually present as painless, gradually enlarging swellings just under the lining of the cheek or hard and soft palate. There is a very high concentration of minor salivary glands on either side of the backmost part of the hard palate. As a result, tumors in these glands frequently arise in this location. Tumors, whether benign or malignant, arising in the major glands are usually nontender and painless. Often the edges of the tumor are quite distinct. Those masses that do not have distinct edges, seem to be stuck to surrounding tissues, and affect adjacent nerves with subsequent loss of feeling or facial or tongue function are usually malignant.

What Are the Causes and Risks? It is unclear if there are any factors which predispose an individual to develop salivary gland malignancies. As opposed to other tumors in the head and neck, smoking does not appear to have any causative relationship.

How to Prevent the Disease: There is no known means of prevention.

How Is It Diagnosed? The initial diagnosis is based upon the physical examination and the location of the mass within or arising from either major or minor salivary glands. Fine needle aspiration is a very important diagnostic and planning tool. With fine needle aspiration, a small gauge needle is placed into the mass, cells are removed from the growth, and then smeared out onto a slide and stained. A pathologist or cytologist examines the slides and very frequently can accurately diagnose the precise nature of the mass. The gland of origin very much determines the level of concern and approach to the lesion. The larger the gland is, the more likely a mass in it will be benign. For example, 80% of masses arising in the parotid are benign, and 20% of them are malignant. In the submandibular gland 50% of the growths are benign, with 50% being malignant. Lastly, masses arising from the minor or sublingual salivary glands are approximately 75% malignant.

Certain malignancies arising in the salivary glands, such as adenoid cystic carcinoma, highgrade mucoepidermoid carcinoma, and squamous cell carcinoma have a propensity to follow along adjacent nerves or metastasize to regional lymph nodes. Should the fine needle biopsy suggest these three particular types of tumors, CT scanning of the neck and face are helpful to try to delineate the precise extent of the tumor and the possibility of regional lymphatic spread. Sialography, where dye is placed into the salivary gland drainage system and an x-ray obtained, is rarely employed, having been replaced by other radiographic studies and fine needle biopsy.

What Are the Long-Term Effects? For those tumors that are clearly benign, e.g., Warthin’s tumors, adenomas, lymphoepithelial lesions, etc., simple observation may be appropriate with the major long-term effect being cosmetic. Should the benign tumor affect drainage of saliva from the gland, symptoms of obstruction or infection can occur. Symptoms of partial obstruction would be an uncomfortable swelling following meals that gradually improves over several hours. Symptoms of complete obstruction typically are persistent pain and swelling of the gland which is intensified with eating. One of the most common types of benign tumors, pleomorphic adenoma, may be observed, however, some of these degenerate into malignancies, particularly adenocarcinoma or adenoid cystic carcinoma. What percentage will become malignant is not exactly clear, but when these tumors degenerate into malignancy, they have often been present for up to 20 years or longer. Indications of malignant degeneration of a previously benign pleomorphic adenoma would be sudden onset of rapid growth and symptoms of pain, facial nerve paralysis, or regional lymphatic metastasis. The long-term effects of the malignant tumors vary based upon the particular cancer that has occurred. Low-grade or mucoepidermoid carcinoma or acinic cell carcinoma are often slow-growing with a small percentage of them metastasizing to regional lymph nodes or involving adjacent structures, such as the facial nerve. High-grade mucoepidermoid carcinomas are usually rapidly growing and have a high percentage of spread to regional lymph nodes and are considered aggressive. Adenoid cystic carcinoma has a rather unique behavior in that it tends to track along adjacent sensory and motor nerves so that whereas the bulk of the tumor may be reasonably small, it may have distant spread along regional nerves so that the area that needs to be removed to attempt a cure may be much larger than the mass that can be felt. Adenoid cystic carcinoma is also unique in that it has a fairly high, five year survival rate with most recurrences showing up as distant metastasis 10 to 20 years after the original diagnosis and treatment.

Am I Putting Others at Risk? No.

What Are the Treatments? For those neoplasms that are clearly benign, observation may be perfectly appropriate. In the case of pleomorphic adenoma, even though it is a benign lesion, because of the possibility that it may become a malignancy, removal is necessary. Simple removal of the pleomorphic adenoma without a surrounding layer of normal parotid is associated with approximately a 60% recurrence rate. Therefore, the preferred form of treatment of a pleomorphic adenoma in the submandibular, sublingual, or minor salivary glands is complete excision of the gland. In the parotid, since most pleomorphic adenomas occur in the superficial aspect of the gland, complete removal of the superficial portion of the parotid, that portion lateral to the facial nerve, is the preferred method of treatment. Removal of the superficial lobe of the parotid reduces the recurrence rate to approximately 4%.
 
Treatment of acinic cell and low-grade mucoepidermoid carcinoma usually involves resection of the entire gland, although in the parotid removal of the superficial portion may be sufficient treatment. These tumors often do not need additional forms of therapy, such as radiation. They can spread to regional lymph nodes, and if involved, a neck dissection will be necessary. If the nodes are not involved, the patient must receive continued surveillance for the possibility of spread. High-grade mucoepidermoid carcinoma and squamous cell cancers, if caught early, may be amenable only to removal of the affected gland. For larger tumors, more extensive resections are required, often sacrificing important structures, such as the facial nerve and its branches in the case of the parotid or lingual and hypoglossal nerves in the case of the submandibular and sublingual glands. If the tumors are particularly large, with or without clinically suspicious lymph nodes, a neck dissection will often be performed followed by radiation therapy. Adenoid cystic carcinomas require complete gland excision, and because the tumor tends to track along nerves, the extent of the dissection is often larger than planned. Since adenoid cystic carcinoma has a strong propensity to follow nerves, sacrifice of extensive portions of the facial nerve should the parotid be involved or lingual and hypoglossal nerves in cases of the submandibular gland are often required. Should resection of the nerve be necessary, immediate nerve grafting can be performed. Adenoid cystic carcinoma may also spread to regional lymph nodes and may necessitate a neck dissection. Radiation therapy is often employed in adenoid cystic carcinoma, and to date there are no effective chemotherapy protocols.

What Are the Side Effects to the Treatments? Should a submandibular gland be removed for benign or malignant disease, the risks to surrounding structures are essentially the same, although risks to the adjacent lingual and hypoglossal nerves certainly are higher in the case of malignancy. Should the hypoglossal or lingual nerves be injured or sacrificed, tongue paralysis and anesthesia will result on that side of the tongue. The main risk with lingual gland resection involves potential injury to the lingual nerve that provides sensation to the tongue or to the duct that drains the submandibular gland. The main risk with parotidectomy, regardless if the tumor is benign or malignant, is injury to the facial nerve. Should the main trunk be injured, then a total facial paralysis will result. If only segments of the nerve after it branches are injured, only those specific portions of the face will be affected. If nerve injury occurs, the nerve should be repaired immediately, if possible, either by direct reconnection or use of nerve grafts. Dry mouth is often not experienced after removal of a single salivary gland. Should radiation therapy be necessary, damage to any remaining salivary glands will occur, with significant dry mouth and the attendant problems of dental caries (cavities).

What Happens After Treatment? For benign tumors no additional therapies are necessary. For malignancies the need for additional treatments is dictated mostly by the specific type of tumor. Each tumor and its behavior also determine the type of follow-up required. More aggressive tumors need longer periods of follow-up, whereas those less aggressive tumors do not need as regular or as prolonged follow-up.

How Do I Monitor the Disease? Any time a mass is noted in the salivary gland or neck, it must be brought to the immediate attention of your physician. Once again the smaller the salivary gland in which the tumor arises, the greater the chance that it will be malignant, and even the benign pleomorphic adenoma has a propensity to degenerate into malignancy. Unless a tumor is convincingly demonstrated to be benign, there is really no role for patient monitoring of salivary gland tumors.

If a patient has a malignant salivary gland tumor that has been treated, self-examination of the neck looking for enlarged lymph nodes, or the region from where the tumor was removed looking for new masses should be performed regularly. Close follow-up and communication with your treating physician is imperative should there be any change in the area in which the tumor was removed. Since some of these malignancies behave aggressively and can spread to distant areas of the body, unexplained weight loss, deep bone pain, headaches or other neurologic symptoms, or masses arising elsewhere need to be followed up immediately with the treating physician.