What is salivary gland cancer?
Salivary gland cancer is a cancer that starts in one of the salivary glands. It is not a single disease. There are actually several different salivary glands found inside and near your mouth. Several types of cancer and benign (non-cancerous) tumors can develop in these glands.
About the salivary glands
Salivary glands produce saliva -- the lubricating fluid found in the mouth and throat. Saliva contains enzymes that begin the process of digesting food. It also contains antibodies and other substances that help prevent infections of the mouth and throat.
The 2 main types of salivary glands are the major salivary glands and minor salivary glands.
There are 3 major salivary glands, which occur in pairs:
- The parotid glands, the largest salivary glands, are found on each side of the face, just in front of the ears. About 7 out of 10 salivary gland tumors start here. Most of these tumors are benign (non-cancerous), but the parotid gland is still where most malignant (cancerous) salivary gland tumors start.
- The submandibular glands are smaller and are found at the back of the jaw. They secrete saliva under the tongue area. About 1 or 2 out of 10 tumors start in these glands, and about half of these tumors are benign.
- The sublingual glands, which are the smallest, are found under the floor of the mouth and below either side of the tongue. Tumors starting in these glands are rare.
In addition, there are several hundred minor salivary glands that are too small to see without a microscope. These glands are located beneath the lining of the lips, tongue, hard and soft palate, and inside the cheeks, nose, sinuses, and larynx (voice box). Tumors in these glands are uncommon, but they are more often malignant than benign. Cancers of the minor salivary glands most often occur in the roof of the mouth (hard and soft palate).
Benign salivary gland tumors
Most salivary gland tumors are benign -- that is, they are not cancerous and do not spread from the salivary gland to other parts of the body. They are almost never life threatening.
There are several types of benign salivary gland tumors, with names such as adenomas, oncocytomas, Warthin tumors, and benign mixed tumors (also known as pleomorphic adenomas).
Benign tumors are almost always cured by surgery. Very rarely, they may become malignant (cancerous) if left untreated for a long time or if they are not completely removed and recur (grow back) several times. How benign tumors become cancers is poorly understood.
Only malignant tumors of the salivary glands will be discussed further in this document.
Salivary gland cancers (malignant salivary gland tumors)
There are many types of salivary gland cancers. Normal salivary glands are made up of several different types of cells, and tumors can start in any of these cell types. Salivary gland tumors are named according to which of these cell types they most look like when viewed under a microscope. The main types of cancers are described below.
There is also a wide range in how quickly salivary gland cancers may grow and spread, with some types tending to grow faster than others. Doctors usually give these cancers a grade (from 1 to 3, or from low to high), based on how abnormal the cancers look under a microscope. The grade gives a rough idea of how quickly the cancer is likely to grow and spread.
- Grade 1 cancers (also called low grade or well differentiated) look very much like normal salivary gland cells. They tend to grow slowly and have a good outcome.
- Grade 2 cancers (also called intermediate grade or moderately differentiated) have an appearance and outlook that is between grade 1 and grade 3 cancers.
- Grade 3 cancers (also called high grade or poorly differentiated) look quite different from normal cells and often grow and/or spread quickly. The outlook (prognosis) for these cancers is usually not as good as for lower grade cancers.
Mucoepidermoid carcinomas are the most common type of salivary gland cancer. Most start in the parotid glands. They develop less often in the submandibular glands or in minor salivary glands inside the mouth. These cancers are usually low grade, but they can also be intermediate or high grade. Low-grade mucoepidermoid tumors have a much better prognosis than high-grade ones.
Adenoid cystic carcinoma
Adenoid cystic carcinoma is usually slow growing and often appears to be low-grade when looked at under the microscope. Still, it is very hard to completely get rid of because it tends to spread along nerves. Adenoid cystic carcinomas tend to come back after treatment (generally surgery and radiation), sometimes many years later. The outlook for patients is better for smaller tumors.
Adenocarcinoma is a term used to describe cancers that start in gland cells (cells that normally secrete a substance). There are many types of salivary gland adenocarcinomas.
Acinic cell carcinoma: Most acinic cell carcinomas start in the parotid gland. They tend to be slow growing and tend to occur at a younger age than most salivary gland cancers. They are usually low grade, but how far they have grown into nearby tissue is probably a better predictor of a patient's prognosis (outlook).
Polymorphous low-grade adenocarcinoma (PLGA): These tend to start in the minor salivary glands. These are usually low grade (as the name states) and are mostly curable.
Adenocarcinoma, not otherwise specified (NOS): When viewed under a microscope, these cancers have enough features to tell that they are adenocarcinomas, but not enough detail to classify them further. They are most common in the parotid glands and the minor salivary glands. These tumors can be of any grade.
Rare adenocarcinomas: Several types of adenocarcinoma are quite rare. Many of these tumor types tend to be low grade and usually have a very good outcome:
- Basal cell adenocarcinoma
- Clear cell carcinoma
- Sebaceous adenocarcinoma
- Sebaceous lymphadenocarcinoma
- Mucinous adenocarcinoma
Other rare adenocarcinomas are more likely to be high grade and may have a less favorable outcome:
- Oncocytic carcinoma
- Salivary duct carcinoma
Malignant mixed tumors
There are 3 types of malignant mixed tumors, carcinoma ex pleomorphic adenoma, carcinosarcomas, and metastasizing mixed tumor. Carcinoma ex pleomorphic adenoma accounts for the vast majority of these cancers. The other 2 are very, very rare. Carcinoma ex pleomorphic adenoma is a cancer that develops from a benign mixed tumor (also known as a pleomorphic adenoma). This tumor occurs mainly in the major salivary glands. Both the grade of the cancer and how far it has spread (stage) are important in predicting the outcome of this tumor.
Other rare salivary gland cancers
Several other cancer types can develop in the salivary glands.
Squamous cell carcinoma: This cancer occurs mainly in older men. It can develop after radiation therapy for other cancers in the area. This type of cancer tends to have a poorer outlook.
Epithelial-myoepithelial carcinoma: This is a rare tumor. It tends to be low grade, but it can come back after treatment or spread to other parts of the body.
Anaplastic small cell carcinoma: The cells in these tumors have nerve-like features. These tumors are most often found in minor salivary glands and tend to grow quickly.
Undifferentiated carcinomas: This group of cancers includes small cell undifferentiated carcinoma, large cell undifferentiated carcinoma and lymphoepithelial carcinoma. These are high-grade cancers that often spread. Overall, the survival outlook tends to be poor. Lymphoepithelial carcinoma, which is much more common in Eskimo and Inuit people, has a slightly better outcome.
Other cancers that can affect the salivary glands
Non-Hodgkin lymphoma: Most non-Hodgkin lymphomas start in lymph nodes. Rarely, these cancers start in immune system cells within the salivary glands. They behave and are treated differently than other types of cancer in the salivary glands. Most lymphomas that start in the salivary glands affect people with Sjögren's syndrome (a disorder that causes immune system to attack salivary gland cells). For more information on lymphomas, see our document called Non-Hodgkin Lymphoma.
Sarcomas: The salivary glands contain blood vessels, muscle cells, and cells that make connective tissue. Cancers that start in these types of cells are called sarcomas. These rarely occur in the salivary gland. For more information on sarcomas, see our document Sarcoma – Adult Soft-Tissue Cancer.
Secondary salivary gland cancers: Cancers that start elsewhere and spread to the salivary glands are called secondary salivary gland cancers. These cancers are not true salivary gland cancers, and are treated based on where the cancer started.
Last Medical Review: 09/21/2012
Last Revised: 09/21/2012