Salivary gland cancer starts in one of the salivary glands. It’s not just a single disease. There are actually several different salivary glands found inside and near your mouth. Many types of cancer and benign (non-cancerous) tumors can develop in these glands.
About the salivary glands
Salivary glands make 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 sets of major salivary glands on each side of the face:
- The parotid glands, the largest salivary glands, are just in front of the ears. About 7 out of 10 salivary gland tumors start here. Most of these tumors are benign (not cancer), but the parotid glands still are where most malignant (cancerous) salivary gland tumors start.
- The submandibular glands are smaller and are below the jaw. They secrete saliva under the tongue. About 1 or 2 out of 10 tumors start in these glands, and about half of these tumors are cancer.
- The sublingual glands, which are the smallest, are under the floor of the mouth and below either side of the tongue. Tumors starting in these glands are rare.
There are also several hundred minor salivary glands that are too small to see without a microscope. These glands are beneath the lining of the lips, tongue, in the roof of the mouth, and inside the cheeks, nose, sinuses, and larynx (voice box). Tumors in these glands are uncommon, but they are more often cancerous than benign. Cancers of the minor salivary glands most often start in the roof of the mouth.
Benign salivary gland tumors
Most salivary gland tumors are benign – that is, they are not cancer and will not spread to other parts of the body. These tumors are almost never life threatening.
There are many 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 cancer if left untreated for a long time or if they are not completely removed and grow back. It’s not clear exactly how benign tumors become cancers.
Only salivary gland cancers 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 cancers are named according to which of these cell types they most look like when seen under a microscope. The main types of cancers are described below.
Doctors usually give salivary 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 it 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 (prognosis).
- 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 very different from normal cells and often grow and/or spread quickly. The outlook 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 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’s very hard to get rid of completely because it tends to spread along nerves. These tumors 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 other 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 tumors tend to start in the minor salivary glands. They usually (but not always) grow slowly and are mostly curable.
Adenocarcinoma, not otherwise specified (NOS): When seen 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 any grade.
Rare adenocarcinomas: Several types of adenocarcinoma are quite rare.
Some of these 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
- Metastasizing mixed tumor
Nearly all of these cancers are carcinoma ex pleomorphic adenomas. The other 2 types are very, very rare.
Carcinoma ex pleomorphic adenoma 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 (its stage) are important in predicting outcome.
Other rare salivary gland cancers
Several other types of cancer 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 rare tumor 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 cell-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
These types of cancer are typically not thought of as true salivary gland cancers, either because they start more often in other parts of the body, or because they start elsewhere and then grow into or spread to 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 from other types of cancers in the salivary glands. Most lymphomas that start in the salivary glands affect people with Sjogren (Sjögren) syndrome (a disorder that causes the immune system to attack salivary gland cells). For more information on lymphomas, see our document 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 treated based on where the cancer started.