Whay is Salivary Gland Tumor?
Salivary glands make saliva, which aids in digestion, keeps your mouth moist and supports healthy teeth. You have three pairs of major salivary glands under and behind your jaw — parotid, sublingual and submandibular. Many other tiny salivary glands are in your lips, inside your cheeks, and throughout your mouth and throat.
Salivary gland tumors can begin in any of your salivary glands. Most are noncancerous (benign), but sometimes they can be cancerous. Most salivary gland tumors occur in the parotid glands. Treatment for salivary gland tumors is usually with surgery to remove the tumor. People with salivary gland cancers may need additional treatments.
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What Is Salivary Gland Tumor?
Salivary gland tumors are abnormal cells growing in the salivary gland or in the tubes (ducts) that drain the glands. Salivary gland tumors can be noncancerous (benign) or cancerous (malignant). Although most salivary gland tumors are benign, some are malignant. It’s also possible for benign tumors to become malignant over time if left untreated.
Malignant salivary gland tumors are relatively rare, making up only 6 percent of head and neck cancers. The most common type of salivary gland tumor (~80% of all salivary gland tumors) is a slow-growing benign tumor in the parotid gland. Minor salivary gland tumors are rare.
Benign Salivary Gland Tumor
There are many types of benign salivary gland tumors. Pleomorphic adenomas (also known as mixed-type tumors) are the most common benign salivary gland tumors. Other benign tumors include papillary cystadenoma lymphomatosum (also known as Warthin tumors), oncocytomas, and adenomas.
Benign Salivary Gland Tumors with Malignant Potential
Pleomorphic adenomas (mixed-type tumors) can undergo malignant transformation, but this usually occurs only after the benign tumor has been present for 15 to 20 years. Once malignant degeneration of a pleomorphic adenoma occurs, it is known as carcinoma ex pleomorphic adenoma. Carcinomatous elements in the tumor metastasize, making carcinoma ex pleomorphic adenoma a highly aggressive tumor with very low cure rates regardless of treatment.
Benign cylindromas can slowly undergo malignant transformation into adenoid cystic carcinomas, the most common malignant tumor of minor salivary glands (and of the trachea). The peak incidence of this malignant tumor is between ages 40 and 60, and symptoms include severe pain and, often, facial nerve paralysis. It has a propensity for perineural invasion and spread, with disease potentially extending many centimeters from the main tumor mass. Lymphatic spread is not common. Pulmonary metastases are common, although patients can live quite long with them.
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Malignant Salivary Gland Tumors
Other malignant tumors are less common and can be characterized by rapid growth or a sudden growth spurt. They are firm, nodular, and can be fixed to adjacent tissue, often with a poorly defined periphery. Eventually, the overlying skin or mucosa may become ulcerated or the adjacent tissues may become invaded.
Mucoepidermoid carcinoma is the most common salivary gland cancer, typically occurring in people in their 20s to 50s. It can manifest in any salivary gland, most commonly in the parotid gland but also in the submandibular gland or a minor salivary gland of the palate. Intermediate and high-grade mucoepidermoid carcinomas may metastasize to the regional lymphatics.
Acinic cell carcinoma, a common parotid tumor, occurs in people in their 40s and 50s. This carcinoma has a more indolent course, as well as an incidence of multifocality.
Symptoms of Salivary Gland Tumors
Symptoms may include:
. Firm, usually painless swelling in one of the salivary glands (in front of the ears, under the chin, or on the floor of the mouth). Swelling can progress at varying rates depending on the underlying cause. Slow swelling usually indicates a benign tumor, while rapid swelling is more likely to indicate a malignant tumor or infection.
. Difficulty moving one side of the face, known as facial nerve palsy. This can signal a malignant and advanced tumor, primarily in the parotid gland.
Causes of Salivary Gland Tumor
Salivary gland tumors are rare. Their cause isn't clear.
Salivary gland tumors begin when some cells in a salivary gland develop changes (mutations) in their DNA. A cell's DNA contains the instructions that tell a cell what to do.
The changes tell the cells to grow and divide rapidly. The abnormal cells go on living when healthy cells would die. The accumulating cells form a tumor.
If additional changes happen in the DNA, the abnormal cells may become cancerous. Cancer cells can invade and destroy nearby tissue. They can also break away from the tumor and spread (metastasize) to distant areas of the body.
Treatment of Salivary Gland Tumors
Surgery, sometimes plus radiation therapy
Treatment of benign tumors is surgery. The recurrence rate is high when excision is incomplete.
For malignant salivary gland tumors, surgery, sometimes followed by radiation therapy, is the treatment of choice for resectable disease. Currently, there is no effective chemotherapy for salivary cancer.
Treatment of mucoepidermoid carcinoma consists of wide excision and postoperative radiation for high-grade lesions. The 5-year survival rate is 95% with the low-grade type, primarily affecting mucus cells, and 50% with the high-grade type, primarily affecting epidermoid cells. Metastases to the regional lymphatics must be addressed with surgical resection and postoperative radiation therapy.
Treatment of adenoid cystic carcinoma is wide surgical excision, but local recurrence is common due to the propensity for perineural spread. Elective nodal treatment is less likely to be required because lymphatic spread is less common. Although the 5- and 10-year survival rates are quite good, the 15- and 20-year rates are worse with many patients developing distant metastases. Lung metastases and death are common, although many years (usually a decade or more) after the initial diagnosis and treatment.
The prognosis for acinic cell carcinoma is favorable after wide excision.
Primary treatment for carcinoma ex pleomorphic adenoma is parotidectomy with the goal of complete resection of all disease A neck dissection is done if there is nodal disease and is considered for some patients without evidence of nodal spread. All surgeries are designed to spare the facial nerve, which is sacrificed only in cases of direct tumor involvement with the nerve.
Types Of Salivary Gland Tumors
Many different types of salivary gland tumors exist. Doctors classify salivary gland tumors based on the type of cells involved in the tumors. Knowing the type of salivary gland tumor you have helps your doctor determine which treatment options are best for you.
. Types of noncancerous (benign) salivary gland tumors include:
. Pleomorphic adenoma
. Basal cell adenoma
. Canalicular adenoma
. Warthin tumor
Types of cancerous (malignant) salivary gland tumors include:
. Acinic cell carcinoma
. Adenoid cystic carcinoma
. Clear cell carcinoma
. Malignant mixed tumor
. Mucoepidermoid carcinoma
. Oncocytic carcinoma
. Polymorphous low-grade adenocarcinoma
. Salivary duct carcinoma
. Squamous cell carcinoma
Salivary Gland Tumor Risk Factors
Factors that may increase your risk of salivary gland tumors include:
. Older age. Though salivary gland tumors can occur at any age, they most commonly occur in older adults.
. Radiation exposure. Radiation treatments for cancer, such as radiation used to treat head and neck cancers, may increase the risk of salivary gland tumors.
. Workplace exposure to certain substances. People who work with certain substances may have an increased risk of salivary gland tumors. Jobs associated with salivary gland tumors include those involved in rubber manufacturing, asbestos mining and plumbing.