Salivary Gland Cancer
Salivary Gland Cancer
Salivary gland cancers begin in the salivary glands of your mouth, cheek, neck or throat. Salivary glands release saliva into your mouth and throat to help digest food and protect against infection.
It is important to note that a growth within a salivary gland or increase in the size of a salivary gland is not necessarily cancer. Changes in a salivary gland can be caused by infections (bacteria and viruses), stones that block up the ducts and make the glands swell, inflammatory problems, systemic diseases or benign (non-cancerous) tumours.
In other words, just because you have an obvious lump or bump (even a tumour) in a salivary gland does not mean it is cancer. Generally, larger salivary glands have a lesser chance that a lump within it is cancer. In fact, most tumours of the salivary gland are benign and can include any of the following:
- Pleomorphic adenoma
- Basal cell adenoma
- Warthin tumour
- Canalicular adenoma
- Sebaceous adenoma
- Ductal papillomas
- Inverted ductal papilloma
- Intraductal papilloma
- Sialadenoma papilliferum
Read below to learn about Salivary Gland Cancer:
Anatomy of Salivary Gland Cancer
In order to begin to understand oral salivary gland cancer, it helps to understand the location, function, and anatomy of the salivary glands. In the head and neck, there are two main categories of salivary glands: major salivary glands (parotid, submandibular, and sublingual glands) and minor salivary glands. The minor salivary glands are much smaller than the major salivary glands. They are not surrounded by envelopes and do not have their own saliva-carrying tubes or ducts.
There are thousands of minor salivary glands in the mouth and throat, but there is a high concentration of them that are located at the junction of the hard and soft palate on the roof of the mouth, near the lips, and along the lining inside the cheeks. There are also minor salivary glands in the tongue, and down into the throat.
Causes of Salivary Gland Cancer
Studies show that individuals have an increased risk of developing oral salivary gland cancer after exposure to high levels of radiation from radioactive explosions or external beam radiation treatment for other cancers.
Certain viruses such as HIV-1, specific types of HPV [types 16 and 18], polyomavirus, and Epstein-Barr virus (EBV) have been suggested to worsen the risk of oral salivary gland cancer. Checking with a doctor may help to determine any increased risk factors.
Signs & Symptoms of Salivary Gland Cancer
Signs & Symptoms
Unlike other cancers of the head and neck, oral salivary gland cancers can typically be seen or felt as an abnormality by a patient, dentist, or doctor. Symptoms to watch for include:
- A lump or bump in the mouth: This is the most common way for an oral salivary gland cancer to present. This is different from the much more common squamous cell carcinomas that present with sores and patches in the mouth. The minor salivary glands are located under the outer-most lining of the mouth, and are called submucosal masses.
- Painful sores or ulcers in the mouth: Oral salivary gland cancer can sometimes grow and become a painful sore or ulcer in the mouth that doesn’t heal after a few weeks.
- Numbness (i.e. in the lower teeth or lower lip/chin area): This means that the cancer cells have invaded the nerves that control the ability to feel.
- Recurrent bleeding from the mouth: Growths in the mouth that are cancer tend to bleed easily when accidentally scraped while brushing teeth or eating certain foods.
- Loose teeth or dentures that don’t fit correctly: This occurs if the tumor invades the tooth sockets or the bones in which the teeth are rooted.
- Difficulty opening the mouth (trismus): This can happen if the cancer invades into any of the muscles that help to open and close the mouth.
- Pain or difficulty with swallowing: This can happen if a tumour becomes so large that it interferes with eating, or invades the muscles and nerves that are used for swallowing.
In rare cases, the first sign of oral salivary gland cancer could be a lump in the neck. This means that the tumour has spread to lymph nodes in the neck. However, in oral salivary gland cancers, the primary cancer in the mouth is usually noticed before it reaches the lymph nodes.
It is important to note that a patient could have one or more of these symptoms and not have oral salivary gland cancer. There are several non-cancerous causes of the same symptoms. That’s why it’s especially important to seek medical advice from a ENT specialist.
Diagnosis of Salivary Cancer
The diagnosis phase can be difficult and overwhelming. During this phase, further testing will be necessary to confirm a diagnosis and determine the best course of treatment. Patients can expect their doctor to have a discussion with them about the risks, benefits, and alternatives to each of the following approaches.
Imaging scans, also known as radiological studies, provide the doctor with an inside view of the body. Imaging of the head and neck will be required to determine the extent as well as the behaviour of a growth, and is a vital step prior to treatment of any tumour in the oral salivary glands. The most common initial imaging tests used are CT and MRI scans. A more advanced imaging study called a PET/CT may also be performed to evaluate if the cancer has spread to other sites in the body, as well as to determine if lymph nodes in the neck are likely to harbour cancer cells.
A biopsy is the removal of a small piece of tissue from the tumour to examine under a microscope and see if it is cancerous. Prior to treatment, patients may need a biopsy of a suspicious lump that has arisen under the lining of their mouth or throat (or mass in the neck). There are a few different ways to perform this biopsy, but the most common and easiest approach is a fine needle aspiration (FNA) biopsy, in which a tiny needle is placed into the tumour and some cells are drawn out through a syringe.
In some cases, imaging and a biopsy may not be necessary. Instead, patients may proceed directly to surgery for both diagnosis and treatment of an oral salivary gland tumour. This approach is more common when cancer is not suspected. Patients can expect their surgeon to have a discussion with them about the risks, benefits, and alternatives to each approach.
Type of Salivary Cancer
After diagnosing a patient with oral salivary gland cancer, a doctor will need to determine what type of cancer it is, as well as the grade of the tumour (i.e. the risk level) based on a biopsy or pathology after surgery. It is important to note that oral salivary gland cancers can be difficult to diagnose. If a doctor is having a hard time determining what type of cancer it is, he or she might ask for a second opinion and send a portion of the tumour off to a specialist in head and neck pathology who deals more frequently with these types of tumours.
Below are the five most common types of oral salivary gland cancer:
- Mucoepidermoid carcinoma: This is the most common type of oral salivary gland cancer (35%). Prognosis for this cancer is highly dependent on the grade of the cancer with low grade having a relatively good prognosis after complete surgical removal.
- Acinic cell carcinoma: This is the second most common type of oral salivary gland cancer, and similar to mucoepidermoid carcinoma, prognosis is closely associated with tumour grade.
- Adenoid cystic carcinoma: This is a slow growing cancer that has a tendency to spread along nerves (perineural spread). While the immediate prognosis for this cancer can be good, it carries a high risk of future recurrence.
- Adenocarcinoma, not otherwise specified: Like the above mentioned oral salivary tumours, this tumor can be low, intermediate, or high grade. The higher the grade of adenocarcinoma, the more likely it is to spread to lymph nodes in the neck or to other sites in the body, requiring additional treatment.
- Carcinoma ex pleomorphic adenoma: This is usually a high grade tumour and tends to progress rapidly, though low-grade variants do exist. Low-grade carcinoma ex pleomorphic adenoma is rare, and may be mistaken for a benign, cellular pleomorphic adenoma. Many patients with carcinoma ex pleomorphic adenoma have a history of a benign growth (pleomorphic adenoma) that then rapidly grows in size. These tumours require multiple treatment modalities, including both surgery and radiation treatment and sometimes chemotherapy.
If a specific cancer diagnosis is not listed above, please click “Other Types of Cancer” to see more possible oral salivary gland cancer types.
Other types of oral salivary gland cancer
- Epithelial-myoepithelial carcinoma
- Clear cell carcinoma
- Basal cell adenocarcinoma
- Sebaceous carcinoma
- Oncocytic carcinoma
- Salivary duct carcinoma
- Myoepithelial carcinoma
- Small cell carcinoma
- Large cell carcinoma
- Lymphoepithelial carcinoma
- Mucinous adenocarcinoma
- Polymorphous adenocarcinoma
- Lymphoma (diffuse large B cell & MALT)
Grade of Salivary Gland Cancer
After the tumour is removed, a doctor will rely on the final pathology of the tumour to determine the grade of cancer. The grade of cancer may determine:
- What type of treatment(s) are necessary
- How much treatment a patient may receive.
“Low-grade” cancers generally require less treatment, and can often be managed with surgery alone. However, “high-grade” cancers often require multiple treatments, such as surgery and radiation. In select circumstances, chemotherapy may also be added with radiation. In other instances, the care team may decide that the cancer is “intermediate-grade” and will provide a treatment plan that is right for the patient.
Stage of Salivary Gland Cancer
The stage of a cancer is determined by the TNM staging system:
- The ‘T’ stands for tumour size.
- The ‘N’ stands for lymph node involvement.
- The ‘M’ stands for distant metastases, or cancer spread to other areas of the body.
Staging helps doctors determine how serious the cancer is and how best to treat it. Staging systems often reference very specific anatomical structures.
Staging is generally based on the American Joint Committee on Cancer (AJCC) 8th edition guidelines. To learn more, see the AJCC TNM Staging Table and the TNM Staging Tool below.
TNM Staging Table, from the American Joint Committee on Cancer (AJCC)
|Any T||Any N||M1||IVC|
Treatment of Salivary Gland Cancer
After determining a diagnosis and completing a full pre-treatment evaluation, doctors will recommend a course of treatment for their patients. In general, there are three different options for the treatment of oral salivary gland cancers that can be used alone or in combination.
For an oral salivary gland cancer, complete surgical removal of the tumour is almost always the first treatment, unless a doctor decides that it is not possible or safe to proceed with surgery. Oral salivary gland cancers may be treated with a soft tissue resection.
If a doctor decides that surgery is a good option, he or she will walk the patient through the risks and extent of the surgery necessary to remove the entire tumour. Reconstruction of the structure involved by the cancer may be required, and will depend on the exact location and the extent of the disease.
If necessary, a surgeon may also perform a neck dissection during surgery or soon after, which involves removing some of the lymph nodes from the neck and checking to see if they contain cancer. This decision will be made based on the pathological diagnosis and the grade of the tumour and whether the surgeon thinks the salivary gland cancer has the potential to spread to the lymph nodes in the neck.
The most common use of radiation for the treatment of oral salivary gland cancers is called adjuvant radiation, which is radiation given after surgery in order to decrease the chances that the tumour will come back.
Reasons for Post-Surgical Radiation
A doctor may recommend post-surgical radiation in a few scenarios.
- If the tumour was not completely removed or if the surgical margins were positive for cancer
- If the type of cancer was determined to be aggressive or of a high grade or T-stage
- If the cancer had spread to lymph nodes or other structures, such as nerves or vessels
In rare cases, complete surgical removal of an oral salivary gland cancer may be impossible or unsafe, and a doctor may recommend radiation therapy as the primary treatment. In this type of treatment, an external beam of radiation, usually a photon beam, is directed at the tumour in order to destroy the rapidly dividing cancer cells. Additionally, a treatment called neutron beam radiation therapy uses high energy neutron beams to treat large slow-growing tumours. This treatment type may be considered for select un-resectable oral salivary gland cancers, such as adenoid cystic carcinoma.
Chemotherapy is not usually effective in treating oral salivary gland cancers but may, in rare cases, be used if the cancer displayed aggressive features, could not be completely removed during surgery, or has spread to other parts of the body outside of the head and neck . Chemotherapy may also be used in combination with radiation therapy in some instances.
Prognosis of Salivary Gland Cancer
A prognosis is a prediction of the outcome of one’s disease. How likely is survival? Will the cancer come back? These are the big questions on most people’s minds after receiving a diagnosis of oral salivary gland cancer. In general, there are several characteristics of the tumour that can inform a patient about their chances of being successfully cured.
Factors That Affect Prognosis
This is the most important factor that affects a patient’s chance of being cured.
The location and extent of the tumour can affect the surgeon’s ability to resect the tumour with adequate margins of healthy tissue around it.
Type and Grade
Both the type and grade of the tumour determine the amount of treatment necessary and the ultimate prognosis.
Spread to Lymph Nodes
This helps determine stage, but even without other factors, spread to lymph nodes in the neck decreases the chance of cure, especially if there is growth of cancer outside of the lymph node.
The ability to completely remove the tumour with a margin of normal tissue around it can be a very important factor in a patient’s prognosis.
Spread into Local Structures
Spread into large nerves, skin and bone has been shown to indicate a worse prognosis.
While each of these factors contributes to one’s outcome, patients should have a discussion with their doctor to determine their overall prognosis. Giving a percentage of survival is challenging because cancer research often looks at multiple types of cancer and may include a large range of patients who underwent a variety of treatments.
What to Expect After Treatment of Salivary Gland Cancer
What to Expect After Treatment
After treatment, patients should follow-up with their doctors on a regular basis.
Patients should visit their head and neck specialist on a regular schedule (or earlier if they have any concerning symptoms). This allows doctors to monitor the patient for any sign that the cancer has returned. The best timeline for follow-up will be determined by the doctor.
Standard Follow-up Schedule
- For the first year, go every 1-3 months.
- For the second year, go every 2-6 months.
- For the third to fifth year, go every 4-8 months.
- After five years, start going once annually.
Doctors may select an imaging scan to be performed in the first 6 months after treatment. The first scan serves as a “baseline” study for the purpose of comparing future studies. This will depend on the type and location of the cancer. Imaging could range from something as simple as a quick chest X-ray, to more extensive tests such as a CT, MRI, or PET scan. If something suspicious comes up, a patient may need a biopsy.