Salivary gland cancers are malignancies that develop in the salivary glands in the mouth. Salivary glands are responsible for the production of saliva, which is a fluid that aids in digestion, prevents your mouth from becoming too dry and supports healthy teeth.
In humans, there are three pairs of major salivary glands located behind the jaw: parotid, sublingual and submandibular. The parotid glands are largest, and are found in the cheeks. The main role of the parotid glands is to initiate the first part of digestion. Most salivary gland cancers develop in the parotid salivary glands. The sublingual glands are the smallest and are found on each side of the tongue. These glands produce the least amount of saliva, and are least likely to have a cancer develop in them. The submandibular glands are located on the floor of our mouths on each side, and produce the most saliva. There are also several minor salivary glands found in the lips, cheeks, mouth, and throat.
Salivary gland cancers are more common in males, and are generally found in people over 50 years of age. However, anyone can develop this disease.
Types of Salivary Gland Cancers
There are several different types of salivary gland cancers, that are categorised by the types of cells they develop from.
Mucoepidermoid Carcinomas (MECs)
Mucoepidermoid carcinomas are the most common type of salivary gland cancer, and usually develop in the parotid glands. They develop from mucoepidermoid cells, which are mucus-secreting cells that line the salivary glands. These cancers are often slow growing, can be aggressive and can have a good prognosis when caught early.
Adenoid Cystic Carcinomas (ACCs)
Adenoid cystic carcinomas are the second most common type of salivary gland cancer, and usually develop in the sublingual or submandibular glands. They develop from the tissues that line the salivary glands, and are often slow growing. ACC can be aggressive, often have a high recurrence rate, and may not have as good of a prognosis as other salivary gland cancers.
Myoepithelial Carcinoma
Myoepithelial carcinomas are a rare form of salivary gland cancer which usually develop in the parotid glands. They develop from myoepithelial cells, which assist in the facilitating movement of saliva in salivary ducts. While some myoepithelial carcinomas can be aggressive, they can have a good prognosis when caught early.
Acinic Cell Carcinomas
Acinic cell carcinomas are a rare form of salivary gland cancer that usually develop in the parotid glands. They develop from acinar cells, which are responsible for the secretion of saliva. Acinar cell carcinomas are often slow-growing, and are more common in females. It generally affects people at a younger age than other types of salivary gland cancers.
Malignant Mixed Tumours
Malignant mixed tumours are tumours that have more than one type of cancer cells in them.
Carcinoma ex Pleomorphic Adenomas
Carcinoma ex pleomorphic adenomas are rare salivary gland tumours, and are often found in the parotid glands. They develop from pleomorphic adenomas, which are benign tumours (adenoma) with many different cell types (pleomorphic). Once these tumours become cancerous, they may grow quickly and become aggressive.
Carcinosarcomas
Carcinosarcomas are very rare salivary gland tumours that contain a mix of carcinoma (cancer arising from tissues that line organs) cells and sarcoma (cancer arising from bones and/or soft tissue) cells. They can be fast-growing, aggressive, and may not have as good of a prognosis as other types of salivary gland cancer.
Polymorphous Adenocarcinomas
Polymorphous adenocarcinomas are rare types of salivary gland cancers that often develop in the sublingual or submandibular glands. They develop from mucus-producing glandular cells (adenocarcinomas) and have various different growth patterns (polymorphous). These cancers are often slow growing, and may have a good prognosis.
Hyalinizing Clear Cell Carcinomas
Hyalinizing clear cell carcinomas (HCCCs) are rare types of salivary gland cancers that often develop from tissues that line the salivary glands. It generally develops from the minor salivary glands of the lips, cheeks, mouth, and throat, however in rare cases it can also develop in major salivary glands, the nasopharynx or the larynx/voice box. Unlike most other salivary gland cancers, HCCCs are slightly more common in females, and are most commonly found over the age of 60. HCCCs are generally not aggressive, rarely metastasise, and can have an excellent prognosis.
Rare forms of Salivary Gland Cancer
These types of salivary gland cancer are very rare:
- Anaplastic carcinomas.
- Basal cell adenocarcinomas.
- Clear cell carcinomas.
- Cystadenocarcinomas.
- Epithelial – myoepithelial carcinomas.
- Lymphomas.
- Mammary analogue secretory carcinoma (MASCs).
- Mucinous adenocarcinomas.
- Oncolytic carcinomas.
- Salivary duct carcinomas.
- Sebaceous adenocarcinomas.
- Sebaceous lymphadenocarcinomas.
- Sialoblastomas.
- Squamous cell carcinomas.
Treatment
If salivary gland cancer is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumour) indicates the size and depth of the tumour.
- N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for salivary gland cancer may include:
- Surgery, potentially including:
- Parotidectomy (removal of part or all of the parotid gland(s)).
- Removal of sublingual salivary gland(s).
- Removal of submandibular salivary gland(s).
- Removal of minor salivary glands(s).
- Facial nerve sacrifice (removal of facial nerve – only for cancers in the parotid gland that has spread to the facial nerve).
- Lateral temporal bone surgery (partial or total removal of temporal bone – only for cancers in the parotid gland that has spread into nearby bone).
- Neck dissection (removal of affected lymph nodes in the neck).
- Supportive surgery, potentially including insertion of feeding tubes (gastronomy tube or nasogastric tube), or a tracheotomy to assist in breathing.
- Chemotherapy.
- Radiation therapy.
- Targeted therapy.
- Immunotherapy.
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Risk factors
While the cause of salivary cancers remains unknown, the following factors may increase your risk of developing the disease:
- Being over 50 years old.
- Previous exposure to radiation.
- Having a history of cancer.
- Having a family history of salivary gland cancer.
- Smoking.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Early symptoms
Possible signs and symptoms of a salivary gland cancer include:
- A lump and/or swelling in the ear, jaw, mouth, lip and/or neck region.
- Pain in the mouth, cheek, jaw, ear and/or neck that doesn’t not go away.
- Facial asymmetry (left and right sides of the face or neck looking different).
- Drooping, numbness and/or muscle weakness one side of the face (palsy).
- Difficulty swallowing.
- Difficulty fully opening your mouth.
- Swelling on one side of the face.
Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have a salivary gland cancer, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Imaging and blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-ray and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Endoscopy & biopsy
An endoscopy is a surgical procedure that involves inserting a long, flexible tube with a light and small camera through your throat, oesophagus and small bowel, in order to examine the lining of the gastrointestinal tract and detect any abnormalities. You will be given a sedative or anaesthetic throughout the procedure. You will be asked to fast for several hours prior to the procedure. An endoscopy is often done as a day surgery. Your doctor will discuss the risks and any possible complications of this procedure prior to the procedure.
Throughout the procedure, your doctor may also perform an endoscopic ultrasound to guide the needle during a biopsy, or to check for signs of cancer metastasis.
If any abnormalities are observed, your doctor will remove a small tissue sample for analysis.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage salivary gland cancers have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.