Salivary glands make and release saliva that lubricates your mouth and throat, starts the digestion of your food, and coats the lining of the upper airway to help protect you from infections. Tumors, either benign (not cancer) or malignant (cancer), can arise in any of these glands.
There are three pairs of major salivary glands:
- Parotid glands Located in front of your ears on either side of your head, these are your largest salivary glands. About 80 percent of salivary gland tumors start in these glands. About 75 percent of these tumors are benign (usually a type called pleomorphic adenomas) and 25 percent are malignant.
- Submandibular glands These are just under your mandible, or jaw bone, about halfway between your chin and your ear. About 10 to 15 percent of salivary gland tumors start here. About half of the tumors arising in these glands are benign and half are malignant.
- Sublingual glands These are in your mouth under your tongue on either side. Tumors are not as common in these glands. The majority of tumors arising in these glands are malignant.
- You also have over 1000 microscopic salivary glands around your head and neck. We call these the minor salivary glands. Tumors in these glands are not common, but when they occur about 25 percent are benign and 75 percent are malignant.
There are many different types of salivary gland tumors, based on the type of cell where the tumor starts:
- Mucoepidermoid carcinoma
- Adenoid cystic carcinoma
- Acinic cell carcinoma
- Adenocarcinoma (either low grade or high grade).
These are the most common examples of malignant tumors, but other types of cancers can occur as well. One way that doctors group malignant salivary gland tumors is by grade. The grade of a tumor is based on how normal the cancer cells look and how quickly they grow or spread.
- Grade 1: Cells look very normal and grow slowly. Outcome tends to be good when doctors can perform a surgical resection (removing the tumor through surgery). Also called low grade or well differentiated.
- Grade 2: Cell appearance and outcome falls between grade 1 and 3. Also called intermediate grade or moderately differentiated.
- Grade 3: Cells look very abnormal and grow or spread quickly. Outcome tends to be poor. Also called high grade or poorly differentiated. Doctors often use radiation therapy in addition to surgery for grade 3 tumors.
Doctors have not been able to link salivary gland tumors to many risk factors (factors that increase your chance of getting a tumor). In most cases, there is no evidence to tell us what caused the DNA changes in the salivary gland cells that led to a tumor. These factors may increase the risk in some cases:
- Having radiation treatment to the head or neck for other reasons
- Being exposed to certain radioactive substances, such as might happen in some industries
- Working with nickel alloy dust or silica dust
- Eating a diet low in vegetables and high in animal fat.