Salivary glands produce saliva, which keeps the mouth moist and supports digestion. Salivary gland cancer is a rare cancer that starts in the tissue of one of these glands.
In this article, we take a closer look at salivary gland cancer, including its symptoms, treatments, and risk factors.
The mouth contains many salivary glands. Some are major, and some are minor. Salivary gland cancer occurs when one of these glands develops a cancerous tumor.
There are three pairs of major salivary glands.
The parotid glands, positioned just in front of each ear, are the largest salivary glands. A tumor is most likely to develop here. While most tumors that develop here are benign, this is also the starting place for most malignant salivary gland tumors.
The sublingual glands sit under the tongue and are the smallest of the major salivary glands. It is rare for a tumor to start in these glands.
The submandibular glands are just below the jaw. Around 10–20% of tumors begin here, and roughly 50% are malignant.
There also hundreds of microscopic minor salivary glands all around the mouth. Locations include:
- the sinuses
- the tongue
- inside the cheeks
- the nose
- the larynx
- voice box
Tumors are less likely to occur in these minor glands, but if one does develop, it is more likely to be malignant.
Salivary gland tumors can include cancers of the blood and lymphatic system, such as non-Hodgkin lymphoma.
Benign tumors do not spread locally or to distant parts of the body. However, without treatment or following incomplete removal, a benign tumor might become malignant. Malignant tumors are more aggressive and have a higher risk of metastasis, or spreading. Surgery often provides a full cure.
Many types of cancer can develop in the salivary glands. Some are adenocarcinomas, which are cancers of cells that secrete substances. Salivary gland cancers include:
- mucoepidermoid carcinomas, which are often slow growing and mostly start in the parotid glands
- adenoid cystic carcinomas, which are also slow growing but may be difficult to cure because they grow along nerves
- acinic cell carcinomas, which more often occur at a younger age and are often slow growing
- polymorphous low grade adenocarcinomas, which are mostly curable and start in the minor salivary glands
Sometimes, doctors can identify that a person has an adenocarcinoma, but cannot identify the type. These are known as adenocarcinoma, not otherwise specified (NOS) and are most common in the parotid and minor salivary glands.
Other rare types of cancer might also develop. For example, sarcomas, which are cancers of connective tissue cells, may develop. However, it is rare for a sarcoma to develop in the salivary glands.
Non-Hodgkin lymphoma, a cancer of immune cells, mostly develops in people who have Sjögren syndrome. This is an autoimmune condition that affects salivary gland cells.
A person who has salivary gland cancer may experience:
- difficulties in opening their mouth completely
- weak facial muscles on one side of the face
- a swelling or lump around the jaw, mouth, or neck area
- a noticeable difference in the shape of one side of the neck or face
- a numb feeling in part of the face
- constant pain in the salivary gland
People should see a doctor about any painless lumps that do not directly result from a known infection.
Several factors can increase the risk of developing salivary gland cancer.
People who have undergone radiation therapy for previous cancers of the head and neck may have a higher chance of developing salivary gland cancer later in life.
Older people also have a higher chance of developing salivary gland cancer, although people of any age can develop it. Males also have a slightly higher risk than females of having salivary gland cancer.
Genetic factors can also increase the risk. However, this is very rare, and doctors do not think that family history contributes to salivary gland cancer in most people.
Workplace exposure to substances, such as nickel alloy dust and silica dust, may also be a factor.
Research continues into other potential risk factors, including cellular phone use, diet, and tobacco and alcohol consumption. However, studies have not yet confirmed the impact of these factors on salivary gland cancer development.
The doctor will ask the person about their medical history and examine the sides of the face, the mouth, and the area around the jaw. If they notice any swelling in the lymph nodes, this could be a sign of cancer.
Muscle weakness or numbness in the face could indicate that the cancer has spread to the nerves.
The doctor may request imaging tests to determine the location and spread of any disease. They may also recommend a biopsy to collect and analyze salivary gland tissue.
In an incisional biopsy, the specialist makes a small cut and removes a sample of the tumor, which they send to a lab for examination.
Depending on the initial findings, they may recommend surgery to remove and test the whole tumor.
Treatment for salivary cancer often involves surgery, radiation therapy, chemotherapy, or a combination of these.
Surgery is normally the primary form of treatment for salivary gland cancer. The surgical team may need to remove the whole salivary gland, along with any nerves and ducts to which the cancer may have spread.
If the tumor is small and easy to access, the surgeon may remove just the tumor and a small amount of surrounding tissue.
In radiation therapy, the cancer care team directs high powered energy particles or beams at a tumor to slow the growth of or destroy cancer cells.
The most common type of radiation therapy for salivary gland cancer is external beam radiation therapy. It provides an intense level of radiation.
A person will usually need radiation treatment every day for 5 days a week. The course of treatment will last for up to 7 weeks.
Newer types of radiation therapy that may be more successful include accelerated hyperfractionated radiation. This breaks treatments up into several smaller doses per day.
A cancer care team might also administer radiosensitizer medications. These make a tumor more sensitive to radiation therapy, meaning that it kills more cancer cells.
A doctor requests chemotherapy when the cancer has spread to other parts of the body. The individual takes medication either by mouth or intravenously to kill the cancerous cells.
A variety of drugs are available that a cancer care team can administer on their own or in combination with other drugs, such as 5-fluorouracil (5-FU), or carboplatin.
Side effects of treatment
Complications of surgery include:
- adverse reactions to anesthetic
- slow wound healing
- excessive bleeding
Nerve damage may cause one side of a person's face to droop, and an individual may have difficulties swallowing or talking after surgery. In some cases, a person can have reconstructive surgery, and a speech therapist can help with restoring some lost eating and speaking functions.
Gustatory sweating, or Frey Syndrome, occurs when nerves grow back in an unusual way. This growth can lead to sweating over some areas of the face when chewing. Further surgery or medication can treat this.
The adverse effects of radiation therapy generally include:
- burning of the skin
These typically resolve after treatment. Radiation therapy can, however, have effects on other parts of the head and neck, including:
- dry mouth due to decreased saliva production
- throat and mouth sores
- dry, sore throat
- difficulty swallowing
- total or partial loss of taste
- bone pain and damage
- worsening of dental problems
- damage to the thyroid gland
- ringing or sensation of fullness in the ears
Chemotherapy kills cancer cells, but it can also affect some healthy cells, such as hair follicles and cells in the lining of the mouth. Common side effects include:
- reduced appetite, nausea, and vomiting
- low white and red blood cell count, increasing the risk of infections and fatigue
- low blood platelet count, leading to easier bruising
- hair loss
- mouth sores
After completing treatment, a doctor will continue to monitor the individual closely. It is important to attend all follow up appointments as this can help to minimize any side effects of treatment and deal with any recurrence early.
Preventing salivary gland cancer is difficult because doctors do not know what causes it.
Avoiding tobacco and alcohol may slightly reduce the risk of this rare cancer and many other more common types.
People working in environments where there is nickel alloy dust, silica dust, or radioactive substances should use appropriate protection.
The prognosis for people with salivary gland cancer depends on how far the cancer has spread from its original site.
The American Cancer Society (ACS) uses a 5-year survival rate as a guide for a person's outlook after a cancer diagnosis. This compares the likelihood that a person with cancer will live for 5 years beyond the date of diagnosis with that of a person who does not have cancer.
If a doctor identifies and treats salivary gland cancer before it spreads from its original site, an individual is 93% as likely to survive for 5 years after diagnosis. If this cancer spreads into nearby tissue, the rate reduces to 67%.
If the cancer spreads to distant sites, the 5-year survival rate is 34%.
However, these vary depending on age, overall health, and the success of treatment. Only a doctor will be able to predict an accurate outlook.
Early diagnosis and treatment are the best ways to improve a person's outlook for salivary gland cancer.